Engineering molecular rotor-stator ligand architectures on copper nanoclusters for efficient photothermal conversion.

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Learn more: PMC Disclaimer | PMC Copyright Notice Nat Commun . 2026 Mar 3;17:3388. doi: 10.1038/s41467-026-70141-8 Search in PMC Search in PubMed View in NLM Catalog Add to search Engineering molecular rotor-stator ligand architectures on copper nanoclusters for efficient photothermal conversion Bingzheng Yan Bingzheng Yan 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China 2 Research Center for Quantum Physics and Technologies, School of Physical Science and Technology, Inner Mongolia University, Hohhot, China Find articles by Bingzheng Yan 1, 2, # , D Sulalith N D Samarasinghe D Sulalith N D Samarasinghe 3 Department of Chemistry, Kansas State University, Manhattan, KS USA Find articles by D Sulalith N D Samarasinghe 3, # , Jing Sun Jing Sun 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Jing Sun 1, # , Hongwen Deng Hongwen Deng 4 New Cornerstone Science Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China Find articles by Hongwen Deng 4 , Lei Li Lei Li 4 New Cornerstone Science Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China Find articles by Lei Li 4 , Ming-Qiang Qi Ming-Qiang Qi 4 New Cornerstone Science Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China Find articles by Ming-Qiang Qi 4 , Fangming Zhao Fangming Zhao 5 Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China Find articles by Fangming Zhao 5 , Qinghua Xu Qinghua Xu 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Qinghua Xu 1 , Huifang Guo Huifang Guo 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Huifang Guo 1 , Xueli Sun Xueli Sun 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Xueli Sun 1 , Xuekun Gong Xuekun Gong 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Xuekun Gong 1 , Rong Huo Rong Huo 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Rong Huo 1 , Mengsi Zhu Mengsi Zhu 6 Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, China Find articles by Mengsi Zhu 6 , Qingyuan Wu Qingyuan Wu 6 Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, China Find articles by Qingyuan Wu 6 , Zhenlang Xie Zhenlang Xie 7 College of Food Science and Engineering, Guangdong Ocean University, Yangjiang, China Find articles by Zhenlang Xie 7 , Chengrui Xin Chengrui Xin 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Chengrui Xin 1 , Yaqi Wang Yaqi Wang 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Yaqi Wang 1 , Xiaotong Jiang Xiaotong Jiang 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Xiaotong Jiang 1 , Simin Li Simin Li 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Simin Li 1 , Fengyu Li Fengyu Li 2 Research Center for Quantum Physics and Technologies, School of Physical Science and Technology, Inner Mongolia University, Hohhot, China Find articles by Fengyu Li 2 , Meng Zhou Meng Zhou 5 Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China Find articles by Meng Zhou 5 , Christine M Aikens Christine M Aikens 3 Department of Chemistry, Kansas State University, Manhattan, KS USA Find articles by Christine M Aikens 3, ✉ , Nanfeng Zheng Nanfeng Zheng 4 New Cornerstone Science Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China 6 Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, China Find articles by Nanfeng Zheng 4, 6, ✉ , Hui Shen Hui Shen 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China Find articles by Hui Shen 1, ✉ Author information Article notes Copyright and License information 1 College of Energy Materials and Chemistry, Inner Mongolia University, Hohhot, China 2 Research Center for Quantum Physics and Technologies, School of Physical Science and Technology, Inner Mongolia University, Hohhot, China 3 Department of Chemistry, Kansas State University, Manhattan, KS USA 4 New Cornerstone Science Laboratory, Collaborative Innovation Center of Chemistry for Energy Materials, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, China 5 Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, China 6 Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province (IKKEM), Xiamen, China 7 College of Food Science and Engineering, Guangdong Ocean University, Yangjiang, China ✉ Corresponding author. # Contributed equally. Received 2025 May 26; Accepted 2026 Feb 19; Collection date 2026. © The Author(s) 2026 Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/ . PMC Copyright notice PMCID: PMC13066518  PMID: 41776155 Abstract Copper nanoclusters represent a promising yet underdeveloped frontier in materials science. Here, we propose a general and efficient strategy for enhancing photothermal conversion efficiency through the incorporation of rotor-stator ligand architectures onto copper nanocluster surfaces. As a representative example, we design carboxylate ligands functionalized with adamantane groups to stabilize a [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 4 H 8 ] 2- nanocluster. In this architecture, the adamantane unit functions as a molecular rotor, while the carboxylate group serves as a molecular stator. The engineered nanocluster achieves a photothermal conversion efficiency of 75%. The adamantane rotors exhibit a lowered rotational energy barrier within the cluster framework, enabling stable and rapid molecular rotation that effectively promotes non-radiative transitions. This mechanism optimizes the conversion of light into thermal energy, enabling the nanocluster to rapidly heat up to 200 °C under 445 nm laser irradiation at a power density of 1.0 W cm -2 . The proposed strategy could be applicable to other rotor types, yielding a broad family of copper nanoclusters with enhanced photothermal conversion capabilities and multifunctional potential. Subject terms: Nanoparticles, Organic-inorganic nanostructures Copper nanoclusters are promising photothermal heaters, but their conversion efficiency is limited efficiency. Here, the authors present a rotor-stator ligand architecture that enables enhanced photothermal conversion efficiency of copper nanoclusters. Introduction Ligand-protected atomically precise metal nanoclusters (APCs) represent a class of hybrid nanomaterials characterized by well-defined metal cores with specific nuclearity and tunable ligand shells that enable precise structural and functional customization 1 – 3 . These nanoclusters exhibit defined chemical composition and atomically resolved molecular structures 4 , 5 , positioning them as a platform for technological applications 6 – 9 . Recent advances have identified APCs as promising photothermal materials, offering a new structural model for understanding structure-property correlations of nanomaterials 10 , 11 . The photothermal conversion efficiency (PCE), a critical performance metric, fundamentally determines their applicability in photothermal therapy, photocatalysis, and related fields 12 . Current strategies for PCE enhancement in APCs primarily employ two synergistic approaches: 1. Ligand engineering: introducing π -conjugated polycyclic aromatic hydrocarbons (e.g., anthracene, naphthalene) as surface ligands to enhance light-harvesting capability and broaden the photoresponse range by leveraging their broad spectral absorption and efficient charge transfer characteristics. However, this approach has notable limitations; optical absorption optimization is often constrained by the lack of a non-radiative transition mechanism, generally yielding only modest PCE values 13 , 14 . 2. Core structural control: designing the geometric configuration of the metal core (e.g., anisotropic rod-like or plate-like structures) to promote directed exciton coupling and enhance the localized surface plasmon resonance effect 15 , 16 . Although this strategy is commonly adopted in metal nanoclusters to enable efficient photothermal conversion, precise control over the morphology of the metal core—especially for copper nanoclusters at their present stage of development—remains a challenge 17 . Copper nanoclusters often incorporate hydride ligands in their structures, which poses significant challenges to the synthesis of specimens with specific shapes 18 , 19 . Our research group holds a continuing interest in the development of copper nanoclusters as photothermal conversion materials 17 . Copper nanoclusters are characterized by their Earth abundance, low cost, tunable optical properties, and distinct structures 20 – 25 . In this context, we propose that the PCE of copper nanoclusters could be strategically enhanced through the strategic amplification of molecular motion. At the fundamental level, thermal energy is intrinsically linked to the kinetic activity of molecules, encompassing both their collective translational movements and internal vibrational/rotational degrees of freedom 26 , 27 . Substantial experimental evidence from previous studies has established a direct correlation between the vigor of molecular motion and the total thermal energy content of a system 28 , 29 . This fundamental principle has been implemented in the design of organic polymer photothermal materials, where researchers have deliberately incorporated structurally dynamic functional groups into the molecular architecture 30 , 31 . Upon photoexcitation, these motile moieties undergo pronounced conformational changes, effectively transducing absorbed luminous energy into thermal energy through their mechanical motion. A demonstration of this approach was reported by Peng’s research group, who achieved a PCE of 88.3% by engineering organic nanoparticles with freely rotating –CF 3 groups 32 . More recently, tetraphenylethylene (TPE) has demonstrated potential as a molecular rotor for constructing gold nanocluster-based photothermal materials 33 . However, the PCE of TPE-functionalized clusters remains limited to ≈ 26%, which may be attributed to the low rotational symmetry and restricted rotational freedom of TPE groups. Following a strategy inspired by the Peng group’s –CF 3 system, the tert-butyl group—which possesses relatively high rotational symmetry—was recently incorporated into the [XCu 54 Cl 12 ( t BuS) 20 (NO 3 ) 12 ] (Cu 54 ) cluster 34 . However, this modification still resulted in only a moderate PCE of ≈ 30%, as performance was limited by several inherent drawbacks of thiol-based stators, including insufficient rigidity, limited stability, and short rotation axes 35 , 36 . These observations collectively underscore the need to design and integrate other rotor-stator synergistic systems that offer greater conformational freedom and exhibit low—ideally negligible—rotational energy barriers. Such improvements are anticipated to enable metal nanoclusters to achieve substantially enhanced PCE. In this study, we report on the design of copper nanoclusters integrated with molecular rotors that exhibit enhanced conformational flexibility to improve PCE. Carboxylate groups function as stators due to their propensity to form chelating coordination motifs, which generate a more rigid “pincer-like” anchoring structure. This configuration substantially constrains rotation or wobbling at the metal-stator bond, establishing a stable and well-defined rotational axis for the attached rotor 37 – 39 . Additionally, the carboxylate stator (R-COO) possesses an extended effective linker that positions the rotor farther from the crowded nanocluster surface 40 , 41 . This design affords greater rotational space and degrees of freedom at the nanoscale, consequently reducing the rotational energy barrier. Various molecular rotors—including adamantane, bicyclo[1.1.1]pentane, biphenyl, azobenzene, and thiophene—were incorporated onto the surface of the copper nanoclusters by engineering the carboxylate ligands. This architecture facilitates stable and rapid rotation of the molecular rotors, effectively promoting non-radiative transitions and resulting in improved photothermal behavior with multifunctional potential in biomedical and optoelectronic applications. For instance, an adamantane-functionalized copper nanocluster, [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 4 H 8 ] 2- (abbreviated as Cu 36 H 8 ), where AdmCOOH denotes 1-adamantanecarboxylic acid and 4-F-PhSH represents 4-fluorothiophenol, demonstrates a PCE of 75%. Results Design and synthesis of adamantane-functionalized Cu 36 H 8 Here, adamantane-functionalized carboxylate ligands were selected to introduce adamantane groups, which are a typical class of molecular rotors, onto the surface of the copper nanocluster. Adamantane serves as a prototypical molecular rotor owing to its well-balanced molecular mass and highly symmetric, nearly spherical geometry 42 , 43 . This structural configuration enables facile rotation, contributes to lattice stability, and reduces undesired parasitic intermolecular interactions due to the absence of a dipole moment 44 . With a moderate rotational frequency, adamantane displays readily observable rotational dynamics while avoiding the instabilities associated with excessively rapid, uncontrolled rotation. Experimentally, the activation energy barrier for its rotation in the solid state is typically found to span from 2.5 to 5 kcal mol -1 45 . The introduction of adamantane groups onto the surface of copper nanoclusters was achieved through our developed copper borohydride-mediated reduction synthetic protocol (see below) 46 . The synthesis of the Cu 36 H 8 nanocluster was accomplished in one pot under ambient conditions, without requiring inert atmosphere protection (see Methods) 47 , 48 . In a typical synthesis, Cu(AdmCOO) 2 was suspended in a mixed solution of methanol and dichloromethane, after which 4-fluorothiophenol was added. After stirring for 10 minutes, a dichloromethane solution of (PPh 3 ) 2 CuBH 4 was added dropwise under vigorous stirring. The mixture was stirred for 5 h at room temperature before the addition of PPh 4 Cl. Stirring was then continued for further 6 hours, yielding a deep brown solution (Supplementary Fig. 1 ). The mixture was centrifuged to discard solid byproducts, and the deep brown supernatant was collected. Subsequently, the supernatant was subjected to ether diffusion, during which the color gradually lightened (Supplementary Fig. 2 ). After two weeks, small block-shaped yellow crystals formed (Supplementary Fig. 3 ). Characterization of Cu 36 H 8 The (PPh 3 ) 2 CuBH 4 used in the synthesis is essential for the formation of the nanocluster, as it serves both as a reducing agent for the conversion of Cu(II) to Cu(I) and as a source of protective ligands to stabilize the resulting clusters 48 . Additionally, the use of PPh 4 Cl in the synthesis is of significant importance. An appropriate amount of PPh 4 Cl provides counterions for the Cu 36 H 8 nanocluster, thereby stabilizing the resulting clusters and enhancing the yield (≈73% based on Cu) (Supplementary Fig. 4 ) 49 . The similar ultraviolet-visible (UV-Vis) absorption spectra of the supernatant and crystalline solutions further confirmed the high purity of the clusters in the crude product (Supplementary Fig. 5 ). The well-crystallized products were initially characterized by mass spectrometry in the negative mode to determine their molecular composition. As shown in Fig. 1a , two main peaks are present in the spectrum of Cu 36 H 8 . The m/z mass interval between neighboring peaks is 0.5, indicating that the cluster carries a −2 charge. Further analysis reveals that these peaks correspond to the molecular formulas [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 4 H 8 ] 2- (experimental value: 3736.10 m/z; theoretical value: 3736.26 m/z) and [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 3 H 8 ] 2- (experimental value: 3605.25 m/z; theoretical value: 3604.92 m/z), respectively. The strong agreement between the experimental and simulated isotopic patterns confirms the assignment. Isotope labeling experiments and mass spectrometry further confirmed the presence of eight hydride atoms in Cu 36 H 8 (Fig. 1b ). Synthetically, the use of (PPh 3 ) 2 CuBD 4 instead of (PPh 3 ) 2 CuBH 4 in the synthesis yields Cu 36 D 8 in a similar amount. The mass spectrum of Cu 36 D 8 also exhibits two prominent peaks, both of which are, as expected, increased by m/z = 4 compared to those of Cu 36 H 8 . The mass spectrometry results unequivocally confirm the presence of eight hydride atoms within the Cu 36 H 8 nanocluster. Fig. 1. Mass spectrometry characterization of the Cu 36 H 8 nanocluster and its deuterated counterpart, Cu 36 D 8 . Open in a new tab a Experimental (black) and simulated (red and dark blue) isotopic distributions of [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 4 H 8 ] 2- and [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 3 H 8 ] 2- . b Experimental (black) and simulated (red and dark blue) isotopic distributions of [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 4 D 8 ] 2- and [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 3 D 8 ] 2- . Source data are provided as a Source Data file. Based on the molecular formula of Cu 36 H 8 , all copper atoms within the cluster are inferred to be in the +1-oxidation state. To confirm this, X-ray photoelectron spectroscopy (XPS) was conducted. The Cu LMM Auger spectrum of the cluster exhibits a distinct peak at 916.25 eV, corresponding to Cu(I) (Supplementary Fig. 6 ) 50 . The Cu 2 p spectrum further supports this conclusion (Supplementary Fig. 7 ). The full XPS spectrum and energy-dispersive X-ray spectroscopy (EDS) mapping reveal the presence and uniform distribution of all elements on the surface of Cu 36 H 8 crystals (Supplementary Figs. 8 , 9 ). Thermogravimetric analysis (TGA) of Cu 36 H 8 indicates a mass loss of about 57% after heating to 400 °C, which corresponds to the loss of all ligands from the cluster (Supplementary Fig. 10 ). These results provide strong support for the compositional assignment of the Cu 36 H 8 nanocluster based on mass spectrometric data. To elucidate the precise structure of the Cu 36 H 8 nanocluster, we first characterized its chemical environment using nuclear magnetic resonance (NMR) spectroscopy. The proton-decoupled 31 P NMR spectrum exhibited a single sharp signal at 23.22 ppm, demonstrating that all phosphine ligands reside in an equivalent coordination environment on the NMR timescale (Supplementary Fig. 11 ). The 1 H NMR spectrum of Cu 36 H 8 exhibits two peaks at 2.49 and 3.76 ppm, which are absent in the 1 H NMR spectrum of Cu 36 D 8 (Supplementary Fig. 12 ). A peak area ratio of 1:1 indicates that two distinct environments with equal populations exist for the eight hydride atoms in the cluster, which is further supported by the 2 H NMR spectrum of Cu 36 D 8 (Supplementary Fig. 13 ). Subsequently, single-crystal X-ray diffraction (SC-XRD) analysis was performed on Cu 36 H 8 at 100 K to further determine its molecular structure (Supplementary Fig. 14 ). The results indicate that Cu 36 H 8 crystallizes in a trigonal unit cell with the R 3 ¯ c space group (Supplementary Tables 1 , 2 ). Cu 36 H 8 exhibits an alternating AB-layered offset arrangement within the unit cell (Supplementary Figs. 15 , 16 ). Additionally, the single-crystal analysis revealed the presence of two PPh 4 + cations surrounding each nanocluster (Supplementary Fig. 17 ), consistent with the −2-charge state of the nanocluster observed in the mass spectrum. Figure 2a–c shows the overall structure of the Cu 36 H 8 nanocluster from different perspectives. Its structure is entirely distinct from that of [Cu 36 H 10 (PET) 24 (PPh 3 ) 6 Cl 2 ] (PET: phenylethanethiolate) reported by Bakr et al., which exhibits a distorted half-cube configuration 51 . The Cu 36 H 8 cluster comprises a tetrahedral-shaped core composed of 36 copper atoms, surrounded by a protective ligand shell formed by 24 thiolate, 4 triphenylphosphine, and 6 carboxylate ligands. These ligands coordinate with the metal core in their respective positions, resulting in the overall structure of the Cu 36 H 8 cluster exhibiting C 3 symmetry (Supplementary Fig. 18 ). As shown in Fig. 2d , the core of Cu 36 H 8 primarily consists of three nested tetrahedral layers, with the outermost tetrahedron oriented opposite to the middle layer and aligned with the innermost layer. These tetrahedral layers, from inner to outer, are designated as Cu 4 -1, Cu 4 -2, and Cu 4 -3, respectively (Supplementary Fig. 19 ). Notably, the innermost Cu 4 -1 layer does not form a perfect tetrahedron, as indicated by the variation in Cu-Cu bond lengths (Supplementary Fig. 20 ). This structural feature explains the observed C 3 symmetry in the overall cluster configuration. The Cu 4 -2 layer surrounds the Cu 4 -1 core, with an average interlayer Cu-Cu bond distance of 3.017 Å between Cu 4 -2 and Cu 4 -1 (Supplementary Fig. 21 ). The Cu 4 -1@Cu 4 -2 assembly is capped by four Cu 3 triangular units, which connect to adjacent Cu 2 subunits (Supplementary Figs. 22 , 23 ). These four Cu 3 triangles and six Cu 2 units collectively constitute a Cu 24 cage structure (Supplementary Fig. 24 ). The combination of the Cu 4 -1@Cu 4 -2 core and the Cu 24 cage forms the Cu 4 -1@Cu 4 -2@Cu 24 framework. This framework further integrates with the outermost Cu 4 -3 layer, completing the Cu 36 H 8 metal framework (Supplementary Fig. 25 ). Fig. 2. Molecule structure of the Cu 36 H 8 nanocluster. Open in a new tab Total structure from the top ( a ), bottom ( b ) and side ( c ) views, respectively. d Anatomy of the metal core of Cu 36 H 8 . e The coordination modes of thiolate ligands on the surface of Cu 36 H 8 . f The coordination modes of phosphine and carboxylate ligands on the surface of Cu 36 H 8 . Color codes for atoms: a red tetrahedron and two dark blue tetrahedra, Cu; green planes, the benzene rings of 4-fluorothiophenol; rose planes, the benzene rings of triphenylphosphine; dark blue spheres, Cu; yellow spheres, S; rose spheres, P; red spheres, O; bright green spheres, F; grey spheres, C. Hydrogen atoms are omitted for clarity. We note that the four copper atoms of Cu 4 -3 are not directly connected to the copper atoms in Cu 4 -1@Cu 4 -2@Cu 24 but are indirectly linked through sulfur atoms, ultimately forming the Cu 36 H 8 core (Supplementary Fig. 26 ). The distribution patterns of thiolate ligands are presented in Fig. 2e . The 24 thiolate ligands exhibit two coordination modes with copper atoms: 12 in μ 3 mode and the remaining 12 in μ 4 mode. Interestingly, the thiolate ligands with different coordination modes display a preferential distribution. The μ 3 -coordinated thiolates are located around the vertices of the Cu 4 -3 tetrahedron, bridging Cu 4 -3 and Cu 4 -1@Cu 4 -2@Cu 24 . In contrast, the μ 4 -coordinated thiolates are uniformly distributed on each face of the Cu 4 -3 tetrahedron (marked in orange) (Supplementary Fig. 27 ). The Cu-S bond lengths between the thiolate ligands and copper atoms range from 2.244 to 2.575 Å. Figure 2f illustrates the coordination modes of the carboxylate and phosphine ligands. Similar to other metal clusters protected by carboxylate ligands, all adamantanecarboxylate ligands adopt a μ 2 coordination mode with copper atoms 52 , 53 . The average Cu-O bond length is calculated to be 2.034 Å. The four PPh 3 ligands also adopt a common coordination mode, positioned at the four vertices of the outermost tetrahedron of the Cu 36 H 8 cluster. We also attempted to propose the locations of the eight hydride atoms in the Cu 36 H 8 cluster. Based on the aforementioned data from mass spectrometry, NMR data, cluster symmetry, and prior knowledge of hydride locations in copper clusters, the positions of the eight hydrides in Cu 36 H 8 were proposed from residue peaks in the difference electron density map of the crystallographic data, and their coordinates were subsequently refined using least-squares methods 54 , 55 . Density functional theory (DFT) calculations were also employed to validate the proposed positions (see below). As shown in Supplementary Fig. 28 , all eight hydrides adopt a μ 4 -coordination mode, residing within the tetrahedral cavities formed by copper atoms. Among them, four hydrides are positioned at the Cu 4 -2 outer layer, exhibiting a displaced tetrahedral coordination. The remaining four hydrides are located between the Cu 4 -1 and Cu 4 -2, displaying a weakly distorted tetrahedral coordination. The average Cu-H bond distance of 1.723 Å is consistent with reported values for copper hydride nanoclusters in ref. 48 . Rotation of adamantane molecules on the surface of Cu 36 H 8 As proof of concept, the rotation of the adamantane groups on the surface of Cu 36 H 8 was subsequently investigated. From an overall structural perspective, the tetrahedral geometry of the Cu 36 H 8 cluster, combined with its compatible ligands, provides ample rotational space for the adamantane groups (Fig. 3a ). The functionalized adamantane carboxylate groups inherently possess rotatable C–C bonds that extend along the rotational symmetry axis of adamantane, forming stable rotation axes (Fig. 3b ). Moreover, the highly symmetric adamantane structural units are less susceptible to interference from surrounding ligands during rotation, which minimizes steric hindrance and thus reduces the rotational energy barrier to the greatest extent. Additionally, the COO - group in the adamantane-functionalized carboxylate ligands allows the adamantane units to adopt a more open, outward conformation, providing even greater rotational freedom. Collectively, these factors create an environment with a low or even negligible rotational energy barrier for adamantane rotation (Fig. 3c ). Fig. 3. The presence of molecule rotors on the surface of the Cu 36 H 8 nanocluster. Open in a new tab a Schematic illustration of rotor rotation in Cu 36 H 8 . b Rotational axis of the 1-adamantane carboxylate ligand. c Schematic representation of low-barrier rotation without hindrance from surrounding ligands. Color codes for atoms: blue tetrahedra, Cu; blue polyhedra, adamantane; green planes, the benzene rings of 4-fluorothiophenol; rose planes, the benzene rings of triphenylphosphine; dark blue spheres, Cu; yellow spheres, S; rose spheres, P; red spheres, O; bright green spheres, F; grey spheres, C. Hydrogen atoms are omitted for clarity. d Stereochemical environment of an adamantane around its adjacent ligands. Distances between hydrogen atoms on adamantane and hydrogen atoms on neighboring ligands. Thiolate ligands around the vertices of Cu 4 -3 ( e ). Phosphine ligands at the vertices of Cu 4 -3 ( f ). Thiolate ligands on the faces of Cu 4 -3 ( g ). Color codes for atoms: blue spheres, hydrogen of adamantane; green planes, the benzene rings of 4-fluorothiophenol; rose planes, the benzene rings of triphenylphosphine; dark blue spheres, Cu; yellow spheres, S; rose spheres, P; red spheres, O; bright green spheres, F; grey spheres, C; white spheres, hydrogen of adamantane thiolate and phosphine ligands. h Variable-temperature 1 H NMR spectroscopy of Cu 36 H 8 in DMF-d 7 . Source data are provided as a Source Data file. Careful analysis of the single-crystal data reveals that the adamantanecarboxylate ligands exhibit rotational states around the C-C axis (Supplementary Fig. 29 ). Observations indicate that the presence of triphenylphosphine and 4-fluorothiophenol ligands does not significantly affect the rotation of the adamantane moiety. As shown in Fig. 3d–g , the adamantane group is surrounded by two μ 3 -coordinated and two μ 4 -coordinated 4-fluorothiophenol ligands, along with two proximal phenyl rings from triphenylphosphine. Apart from van der Waals forces, no other significant interactions influence the adamantane rotor. The average distance between the hydrogen atoms on the adamantane and the nearest hydrogen atoms of surrounding groups is ≈2.644 Å, which significantly exceeds the typical H-H van der Waals interaction distance (2.2–2.4 Å) 56 . Moreover, the limited number of hydrogen atoms around the adamantane rotor is insufficient to create notable hindrance. Therefore, the steric constraints imposed by the ligands are almost negligible, meaning the rotation of the adamantane rotor can be considered essentially unhindered. The rotational dynamics of the adamantane units in Cu 36 H 8 were investigated by variable-temperature 1 H NMR spectroscopy in the range of 233 to 293 K. As shown in Supplementary Fig. 30 , the adamantane proton resonances of uncoordinated 1-adamantanecarboxylic acid at 293 K are located near 2 ppm (2.02, 1.91, 1.72 ppm, with an intensity ratio of 1:2:2). In contrast, the adamantane proton signals in Cu 36 H 8 (Supplementary Figs. 31 , 32 ) exhibit a similar intensity ratio but are shifted downfield as a whole due to the electronic effects upon carboxylate coordination. The key dynamic evidence comes from the observation of the specific methylene protons (H C , the hydrogens on the methylene group farthest from the carboxyl group). As depicted in Fig. 3h , the H C signal in the coordinated state appears significantly smoother even at low temperatures. Upon heating, this signal evolves from four distinct peaks into a broadened doublet. This progression indicates that the exchange of proton environments enters the fast exchange regime after coordination, directly demonstrating a significant reduction in the rotational energy barrier of the adamantane rotor and a further increase in its rotational speed with rising temperature. We attribute the lowering of the rotational energy barrier to the electronic restructuring of the carboxylate upon coordination to the copper cluster core: the C=O bond character is weakened, and the negative charge is delocalized across the metal-ligand bonds. This reduces the intrinsic polarity of the carboxylate and enhances the overall symmetry of the rotor unit, thereby substantially diminishing the hindrance to rotation. To further verify the low rotational energy barrier of the coordinated adamantane-based rotor, we performed variable-temperature 1 H T 1 relaxation NMR measurements on Cu 36 H 8 (Fig. 4a ). The data revealed a positive correlation between the T 1 relaxation time and temperature across the entire measured temperature range. The minimum T 1 value (the peak) for Cu 36 H 8 was observed at a temperature higher than 293 K. The rotational energy barrier of the rotor in Cu 36 H 8 was calculated to be ≈ 1.17 kcal mol −1 using the Arrhenius equation 57 . This represents a very low activation energy, indicating minimal hindrance to the rotor’s motion within the Cu 36 H 8 cluster and highly free rotation. These results further confirm that the adamantane-based rotor in Cu 36 H 8 exhibits a low rotational energy barrier throughout the entire measured temperature range, thereby demonstrating that the coordinated adamantane rotor possesses a low rotational energy barrier and rapid dynamics. For comparison, the Cu 54 cluster containing another type of molecular rotor (tert-butyl) showed a much higher rotational energy barrier of 2.02 kcal mol −1 (Fig. 4b ) 34 . Fig. 4. Theoretical and experimental investigations of the adamantane rotors in Cu 36 H 8 nanocluster. Open in a new tab Experimentally determined spin-lattice relaxation rates (1/ T 1 ) of Cu 36 H 8 ( a ) and Cu 54 ( b ) in DMF-d 7 from 233 to 293 K. c Molecular orbital energy level diagram and the corresponding HOMO and LUMO of the Cu 36 H 8 nanocluster (iso-surface value = 0.01). d Relative energy of the Cu 36 H 8 nanocluster in the ground and excited states as a function of the rotation of adamantane group #1. The dihedral angle is defined by the oxygen atom relative to the C-C-C plane of the 1-adamantane carboxylate ligand, as illustrated. Color code: H, blue; C, gray; O, red. e Transient absorption data map of Cu 36 H 8 in DMF, pumped at 400 nm and probe at 530 nm. f Plot and fitting of kinetic delay traces. ∆ A , changes in absorbance; mOD, milli–optical density units. g Schematic illustration of the internal energy diffusion pathway and the electronic relaxation mechanism in Cu 36 H 8 , as derived from transient absorption measurements. Color codes for atoms: blue tetrahedra, Cu; blue polyhedra, adamantane; green planes, the benzene rings of 4-fluorothiophenol; rose planes, the benzene rings of triphenylphosphine; dark blue spheres, Cu; yellow spheres, S; rose spheres, P; red spheres, O; bright green spheres, F; grey spheres, C. Hydrogen atoms are omitted for clarity. Blue glow represents kernel relaxation, while red glow represents rotational motion relaxation. Source data are provided as a Source Data file. Our theoretical computations show that the Cu 36 H 8 nanocluster exhibits interesting electronic properties near the HOMO-LUMO region, with an energy gap of 3.25 eV at the B3LYP/DZ level of theory (Fig. 4c ). This overestimates the experimental gap, which is common for the hybrid B3LYP functional with similar nanoclusters. The HOMO orbital primarily derives from copper d atomic orbitals combined with p atomic orbitals from sulfur atoms in the thiolate ligands, demonstrating metal-ligand character, which is expected for this system with zero delocalized “superatomic” electrons. This mixed metal-ligand contribution pattern continues from HOMO-1 to HOMO-5. Examining the unoccupied orbitals, LUMO and LUMO + 1 display prominent p and s orbital characteristics around copper atoms, while LUMO + 2 through LUMO + 5 shift significantly to ligand-dominated contributions, particularly exhibiting antibonding π orbitals on the phenyl rings of the triphenylphosphine ligands (an illustration of the atomic orbitals near the HOMO-LUMO region is shown in Supplementary Fig. 33 , alongside a comprehensive breakdown of atomic orbital contributions provided in Supplementary Table 3 ). With these insights, we performed a rotational analysis on all six adamantane groups via the rotatable C-C bond on the 1-adamantane carboxylate ligands (dihedral angles were measured using O-C-C-C as depicted in Fig. 4d . Initial dihedral angles and the selected O-C-C-C atom labels with respect to the crystal structure are provided in Supplementary Table 4 ). In a perfect tetrahedral model, we would expect only a single environment for the adamantane rotor, which would exhibit the same energy barrier. Notably, in its ground state, the Cu 36 H 8 nanocluster shows a relatively low energy barrier in the range of 1.60–3.17 kcal mol −1 during the adamantane group rotations, indicating low-barrier rotational movement. This also reflects the fact that there is a slight variation in the energy barriers for the six different adamantane groups, indicating that the environments of these groups differ slightly based on the single crystal structure geometry. Figure 4d illustrates the relative energy of Cu 36 H 8 nanocluster with respect to the adamantane group #1 rotation, which exhibits an energy barrier of 3.17 kcal mol −1 in the ground state (the other five individual adamantane group rotations are provided in Supplementary Fig. 34 ). Further information on the energy barriers of individual adamantane groups is provided in Supplementary Table 4 . To examine whether these low-barrier rotations persist in excited states, we employed simplified time-dependent DFT (sTDDFT). Our calculations revealed that the S 1 state exhibits a comparable energy barrier range of 1.58–3.16 kcal mol −1 , while maintaining a steady energy gap (61.61 kcal mol −1 ) between S 0 and S 1 states (with excitation at 464 nm and an oscillator strength measuring 0.0025 arb.u.). The S 8 state, which aligns with the experimentally observed absorption peak near 450 nm (theoretically calculated at 448 nm with an oscillator strength of 0.0065 arb.u.), similarly displayed an energy barrier range of 1.60–3.17 kcal mol −1 during adamantane rotations, alongside a consistent 63.87 kcal mol −1 energy gap between S 0 and S 8 states (individual adamantane group energy barriers are provided in Supplementary Table 4 ). These comparable findings across both ground and excited state potential energy surfaces conclusively demonstrate the low-barrier rotational characteristics of the adamantane rotors within the cluster. To further investigate the photothermal conversion process, we also studied the energy conversion mechanism using transient absorption spectroscopy. The excited state absorption decay profile obtained under 400 nm pump laser excitation is shown in Fig. 4e . Biexponential fitting revealed that the relaxation dynamics of excited Cu 36 H 8 involve two distinct lifetime processes (Fig. 4f ). We attribute the shorter decay lifetime of 3.13 ps to internal conversion and core relaxation, as Cu 36 H 8 converts absorbed photons into excitons, which recombine non-radiatively and rapidly generate lattice vibrations within the core within a few picoseconds. The longer decay lifetime of 125.03 ps is attributed to rotor rotational relaxation. The presence of adamantane rotors enables efficient release of energy transferred from the metal core through rotational motion of the rotor structure, which typically occurs on a time scale of tens to hundreds of picoseconds. Changes in the density of states between the metal core and the adamantane rotors of Cu 36 H 8 support the transfer of exciton energy from the core to the rotors. The simulated energy diffusion pathway and electronic relaxation scheme in Cu 36 H 8 illustrate the energy transformation during the photothermal process, which includes three key stages: absorption, core relaxation, and energy release via rotors (Fig. 4g ) 58 . When Cu 36 H 8 absorbs photons, excited electrons are generated. These electrons are converted into vibrational energy of the metal atoms in the core through processes including internal conversion and core relaxation. The energy is then transferred to the rotor groups via phonon scattering and thermalization processes, and finally converted into thermal energy through rotor rotation, which is macroscopically dissipated into the environment as heat exchange and thermal radiation. Photothermal properties of rotor-functionalized Cu 36 H 8 The presence of low-barrier rotors is believed to enhance the PCE of Cu 36 H 8 . Therefore, we investigated its photothermal performance based on the absorption spectrum of Cu 36 H 8 . Cu 36 H 8 appears pale yellow in dichloromethane, with two distinct peaks at 239, 265, and 445 nm in the UV-Vis spectrum (Supplementary Fig. 35 ). The solid-state UV-Vis-NIR absorption spectrum exhibits distinct absorption peaks near 300 and 450 nm, while no significant absorption is observed in the near-infrared region (Supplementary Fig. 36 ). Notably, Cu 36 H 8 demonstrates high stability under ambient conditions. The UV-Vis absorption spectrum of Cu 36 H 8 in dichloromethane shows minimal change over 7 h in air (Supplementary Fig. 37 ). We investigated the photothermal properties of Cu 36 H 8 under 445 nm laser irradiation. The maximum temperatures reached by Cu 36 H 8 at different laser power densities showed a positive correlation with power density, with a turning point observed at 1.0 W cm −2 (Fig. 5a ). As shown in Fig. 5b,c , Cu 36 H 8 crystals achieved their maximum temperature almost instantaneously (within 2 s) under laser irradiation, reaching 200 °C at 1.0 W cm −2 . Even without considering repeatability, the crystals could reach temperatures as high as 300 o C under short-term laser irradiation (2.0 W cm −2 ). Based on the relationship between Cu 36 H 8 and laser power density in Fig. 5a , effective photothermal stability was observed within 1.0 W cm −2 (200 °C). We evaluated the photothermal cycling stability of Cu 36 H 8 at a power density of 1.0 W cm −2 , which demonstrated excellent stability even after nine cycles (Fig. 5d ). TGA under different heating programs confirmed the thermal stability of Cu 36 H 8 up to 200 °C (Fig. 5e and Supplementary Fig. 38 ). Solid-state absorption spectroscopy further indicated the photothermal stability of Cu 36 H 8 within the 1.0 W cm -2 condition (Fig. 5f ). The Cu 36 H 8 rotor, with its low rotational energy barrier, exhibited robust stability and rapid heating, suggesting that the absorbed light energy was efficiently converted into heat through non-radiative pathways. Fig. 5. Photothermal properties of the Cu 36 H 8 nanocluster. Open in a new tab a Photothermal curve of Cu 36 H 8 crystals as a function of laser power intensity under 445 nm laser irradiation. b Time-dependent photothermal curves of Cu 36 H 8 crystals under 445 nm laser irradiation at power densities of 0.1, 0.5, 1.0, 1.5, and 2.0 W cm −2 , respectively. c Infrared thermal images of Cu 36 H 8 crystals at various laser power densities. d Photothermal heating and natural cooling cycles of Cu 36 H 8 under 445 nm laser irradiation at a power density of 1.0 W cm −2 . e Thermogravimetric curves of Cu 36 H 8 . Heating program: 20–400 °C at 10 °C min −1 , with a 5-min isothermal hold at each temperature plateau (25, 50, 75,…, 400 °C). f UV-Vis absorption spectra of Cu 36 H 8 crystals irradiated by a 445 nm laser at various power densities. g Time-dependent photothermal curve of a Cu 36 H 8 solution (2 mg mL −1 in DMF) under 445 nm laser irradiation. h Time-ln θ linear curve of the Cu 36 H 8 solution (2 mg mL −1 in DMF) after 445 nm laser irradiation ( θ is dimensionless). Temperature evolution curves of solid-state Cu 36 H 8 : i Under different electrical powers. The inset is the photo of the Cu 36 H 8 solid photothermal test sample. j Under a 445 nm laser power of 0.117 W. k Linear fitting curves of Cu 36 H 8 at different electric powers to calculate H * . l Photothermal curve of Cu 36 H 8 crystals as a function of power intensity under simulated sunlight irradiation. m Visible light and infrared thermal images of Cu 36 H 8 under 1.0 W cm −2 simulated sunlight irradiation. n A comparison of ignition times between bare and Cu 36 H 8 -coated matches under 445 nm laser irradiation at varying power intensities. Data are presented as mean values ± SD ( n = 3 independent matches; each match represents an independent experimental unit). Statistical significance was determined by a two-tailed Welch’s t -test, with all comparisons showing p < 0.001. Inset images show representative bare and coated matches, with scale bars of 50 mm and 9 mm, respectively. Source data are provided as a Source Data file. Therefore, we conducted an in-depth study on the PCE of Cu 36 H 8 . Considering the solubility of Cu 36 H 8 and the volatility and boiling points of solvents, we selected DMF and DMSO to evaluate its photothermal performance in solution (solvent effects were excluded, Supplementary Fig. 39 ). Under 445 nm laser irradiation, a 2 mg mL −1 solution of Cu 36 H 8 reached ≈ 59 and 81 °C (DMF) and 62 and 85 °C (DMSO) at power densities of 0.5 and 1.0 W cm −2 , respectively (Fig. 5g and Supplementary Fig. 40 ), while demonstrating excellent stability (Supplementary Figs. 41 , 42 ). Through repeated experiments and detailed analysis of cooling curves, the average PCE of Cu 36 H 8 was determined to be ≈ 75% (Fig. 5h ). This value surpasses most other photothermally active nanoclusters reported to date 59 . Additionally, we employed the photothermal and electrothermal equivalence (PEE) method to measure PCE of Cu 36 H 8 in the solid state 60 . By analyzing the temperature changes of the sample under different electrical heating powers (Fig. 5i ), we derived the heat dissipation coefficient through linear fitting at thermal equilibrium and ultimately calculated a PCE of ≈ 77% for Cu 36 H 8 (Fig. 5j, k ). The high PCE further confirms that the adamantane carboxylic acid ligands, acting as molecular rotors, effectively dissipate absorbed photons as heat. This demonstrates that low-energy-barrier rotors are beneficial for developing cluster materials with imrpoved PCE. To further elucidate the critical role of adamantane carboxylate ligands in photothermal performance, we designed comparative cluster systems focusing on three aspects: adamantane as a rotor, carboxylate as a stator, and their synergistic interaction (see Methods). (1) Adamantane functions as an efficient molecular rotor due to its highly symmetrical cage structure, which enables low-barrier, near-isotropic rotation. Replacing adamantane with a triphenylmethyl group in Cu 36 reduced the photothermal temperature increase by half, underscoring the rotor’s advantage (Supplementary Figs. 43a –d, 44 , and Supplementary Table 5 ). (2) The carboxylate group serves as a key stator. Its chelating binding mode expands rotational space and lowers the energy barrier. Introducing three adamantane carboxylate ligands into Cu 29 elevated the temperature increase from ≈100 to ≈160 °C, confirming the stator’s role in facilitating rotation (Supplementary Figs. 43e –h, 45 , and Supplementary Table 6 ). (3) Direct interaction between the rotor and stator is essential. In Cu 14 -2, where these components are decoupled, the improvement was limited. However, anchoring adamantane via carboxylate in Cu 14 -1 significantly enhanced photothermal performance, demonstrating that a synergistic rotor-stator design is crucial for high-efficiency photothermal conversion (Supplementary Figs. 43i –l, 46 , and Supplementary Table 7 ). Since the Cu 36 H 8 cluster can efficiently convert light energy in the blue spectral region into thermal energy, and blue light accounts for ≈ 30% of the total energy in natural sunlight, we consider this material highly suitable for laser-driven heating applications, and it may also exhibit fair photothermal performance under natural sunlight. Tests under simulated sunlight at various power densities (Fig. 5l, m ) demonstrated that Cu 36 H 8 can reach a high temperature of 64 °C at 1.0 W cm −2 irradiation. Additionally, the crystal exhibited high stability under ambient natural light: the absorption spectrum remained nearly unchanged over 53 days of exposure to sunlight in air at room temperature (Supplementary Fig. 47 ). Laser ignition experiments showed that matches coated with Cu 36 H 8 ignited about twice as fast as untreated matches under 445 nm laser irradiation (Fig. 5n ). This enhancement in ignition efficiency was even more pronounced at lower optical power densities, highlighting the advantageous role of the Cu 36 H 8 coating under reduced irradiation conditions. These results, together with its high PCE, high stability, and high-yield synthesis process, underscore the significant practical potential of Cu 36 H 8 for applications such as laser ignition 29 , 61 . Molecular rotor approach enriches copper nanoclusters Building upon the low-barrier rotor strategy, we further expanded the structure and functionality of copper nanoclusters through tailored molecular design. First, another copper nanocluster incorporating adamantane-1-carboxylate rotors ([Cu 23 (AdmCOO) 2 (Ph-S) 16 (PPh 3 ) 6 ] 2+ , denoted as Cu 23 ) was synthesized and demonstrated high photothermal conversion performance, further validating the role of such rotors in enhancing photothermal performance (Fig. 6a–d , Supplementary Figs. 48 – 50 , and Supplementary Table 8 ). To explore structural versatility, we subsequently introduced the nearly spherical [bicyclo[1.1.1]pentane] (BCP) carbon cage as a rotor, synthesizing the Cu 16 O 4 (BCPCOO) 14 (BCPCOOH) 2 (CH 3 O) 10 (Cu 16 ) cluster (Fig. 6e, f , Supplementary Figs. 51 , 52 , and Supplementary Table 9 ) 62 . This material exhibits significant absorption in both the blue and near-infrared regions, and under 445 and 808 nm laser irradiation, it achieves maximum temperatures of 203 and 166 °C, respectively (Fig. 6g, h and Supplementary Fig. 53 ). Finally, by integrating classic chromophoric motifs such as biphenyl, azobenzene, and thiophene as functional rotors, we constructed the Cu 50 series of clusters (Cu 50 (BBC) 10 (4-F-PhS) 20 (PPh 3 ) 6 H 2 (Cu 50 -1), Cu 50 (PABA) 10 (4-F-PhS) 20 (PPh 3 ) 6 H 2 (Cu 50 -2), and Cu 50 (TAA) 10 (4-F-PhS) 20 (PPh 3 ) 6 H 2 (Cu 50 -3) (Fig. 6i–n , Supplementary Figs. 54 – 56 , and Supplementary Tables 10 – 12 ) 63 , 64 . These materials exhibit robust absorption and photothermal performance in the first near-infrared window (NIR-I), with some members (Cu 50 -1 and Cu 50 -2) extending absorption into the second near-infrared window (NIR-II, ≈ 1700 nm) (Fig. 6o, p ). This series, based on the low-barrier rotor strategy, not only enriches the material library derived from this approach but could also enhance the potential of cluster materials for practical applications such as biological therapy, solar-driven thermal storage, and solar-driven seawater evaporation 65 . Fig. 6. Molecular rotor approach for enhancing the structure and functionality of copper nanoclusters for photothermal conversion. Open in a new tab Molecular structure of Cu 23 ( a ), Cu 16 ( e ), Cu 50 -1 ( l ), Cu 50 -2 ( m ), Cu 50 -3 ( n ), and its corresponding rotor ( b , f , i – k ). UV–Vis–NIR diffuse reflectance spectra of the Cu 23 ( c ), Cu 16 ( g ), and Cu 50 -1, Cu 50 -2, Cu 50 -3 ( o ) in the solid state. Time-dependent photothermal curves of Cu 23 ( d ), Cu 16 ( h ), and Cu 50 -1, Cu 50 -2, Cu 50 -3 ( p ) at power densities of 1.0 W cm −2 . All Cu 50 samples were measured under 808 nm laser irradiation. Color codes for atoms: dark blue spheres, Cu; gold spheres, S; rose spheres, P; red spheres, violet spheres and yellow spheres, O; light green spheres, F; blue spheres, N; grey spheres and orange spheres, C. Hydrogen atoms are omitted for clarity. Source data are provided as a Source Data file. Discussion This study developed functional copper nanocluster materials through a surface engineering strategy. Specifically, by introducing rotor groups on the surface of copper nanoclusters through the carboxylate stator, we demonstrated that “low-energy-barrier molecular rotor” functionalization can enhance their photothermal conversion performance. Taking the adamantane-modified [Cu 36 (4-F-PhS) 24 (AdmCOO) 6 (PPh 3 ) 4 H 8 ] 2- cluster as a model, we systematically investigated its design principles, synthesis methods, structural characteristics, molecular rotational dynamics, and photothermal conversion properties. Crystal structure analysis, variable-temperature 1 H NMR spectroscopy, DFT simulations, and transient absorption spectroscopy revealed that the adamantane groups in this cluster exhibit low-energy-barrier rotational characteristics, which facilitate efficient non-radiative transition processes, thereby converting light energy into heat. A PCE of 75% was achieved. Additionally, this strategy enables the introduction of various types of molecule rotors, enriching both the structure and functionality of copper nanoclusters for photothermal conversion. Methods Materials 1-Adamantane carboxylic acid (AdmCOOH, 98%), triphenylacetic acid copper (TPAA, 97%), bicyclo[1.1.1]pentane-1-carboxylic acid (BCPCOOH, 98%), 4-biphenylcarboxylic acid (BBC, 98%), 4-(phenylazo)benzoic acid (PABA, 98%), 3-(2-theinyl)acrylic acid (TAA, 95%), benzoic acid (PhCOOH, 99%), sulfate pentahydrate (CuSO 4 ·5H 2 O, 99%), copper(I) tetra (acetonitrile) tetrafluoroborate (Cu(MeCN) 4 BF 4 , 97%), cupric nitrate (Cu(NO 3 ) 2 , 99%), 4-fluorothiophenol (4-FC 6 H 4 SH, 97%), tetraphenylphosphonium tetraphenylborate (PPh 4 BPh 4 , 98%), 2-methyl-2-propanethiol (C 4 H 10 S, 98%), diphenyl disulfide (C 12 H 10 S 2 , 95%), adamantane-1-thiol (AdmSH, 95%), sodium hexafluoroantimonate (NaSbF 6 , 98%), sodium borohydride (NaBH 4 , 99%), and bis-(triphenylphosphine)-cuprous borohydride ((PPh 3 ) 2 CuBH 4 , 98%) were purchased from Bidepharm. (Shanghai, China). Tetraphenylphosphonium chloride (PPh 4 Cl, 97%) was purchased from Aladdin. (Shanghai, China). Dichloromethane (CH 2 Cl 2 , analytical reagent (A.R.) grade, ≥99% purity), methanol (CH 3 OH, A.R.), N , N -dimethylformamide (C 3 H 7 NO, A.R.) and ether (C 4 H 10 O, A.R.) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). All other reagents were used as received without further purification. Cu(AdmCOO) 2 , Cu(TPAA) 2 , Cu(MeCN) 4 BF 4 , Cu(PhCOO) 2 , Cu(BCPCOO) 2 , Cu(BBC) 2 , Cu(PABA) 2 and Cu(TAA) 2 were prepared according to the methods in ref. 66 . Synthesis of Cu 36 H 8 Cu(AdmCOO) 2 (42.2 mg, 0.10 mmol) was dissolved in a mixture of DCM and methanol (1:1 v/v, 2 mL), yielding a homogeneous blue suspension. To this solution, a DCM solution of 4-fluorothiophenol (7.68 μL, 0.072 mmol in 0.5 mL DCM) followed by a solution of bis(triphenylphosphino)cuprous borohydride (40 mg in 0.5 mL DCM) was added sequentially under vigorous stirring. The reaction mixture underwent a distinct color evolution from blue to yellow-green, then to orange, and finally to deep red. After stirring for 5 h, tetraphenylphosphonium chloride (5 mg) was added, and stirring was continued for another 6 h. The resulting mixture was centrifuged at 10,000× g for 3 min to discard solid byproducts, and the deep brown supernatant was collected. Yellow crystals were obtained by slow diffusion of diethyl ether (about 5 mL) into the supernatant over a period of two weeks. Cu 36 -2 was synthesized in a manner similar to Cu 36 H 8 , except that Cu(TPAA) 2 was used as the precursor instead of Cu(AdmCOO) 2 . Synthesis of Cu 54 The Cu 54 nanocluster was synthesized according to a method reported in ref. 34 . Cu(NO 3 ) 2 (24 mg, 0.189 mmol) was dissolved in DCM (1 mL). Under vigorous stirring, C 4 H 10 S (5.6 μL, 0.05 mmol in 1 mL DCM) was added to the solution. A methanol solution of the reducing agent NaBH 4 (50 mg, 1.32 mmol in 1 mL MeOH) was added all at once, resulting in immediate vigorous gas evolution. After stirring for 2 h, PPh 4 BPh 4 (20 mg, 0.030 mmol in 1 mL DCM) was added. Stirring was continued for another 3 h. The resulting mixture was then centrifuged at 10,000× g for 3 min, and the supernatant was collected. The solution was subjected to diethyl ether diffusion at room temperature. After two weeks, red block-shaped crystals were obtained. Synthesis of Cu 29 -1 Cu(AdmCOO) 2 (42.2 mg, 0.10 mmol) was dissolved in a mixed solvent of DCM and methanol (2 mL). Under vigorous stirring, a DCM solution of AdmSH (17 mg, 0.1 mmol in 0.5 mL DCM) was added to this solution, followed by a solution of bis(triphenylphosphine)copper(I) borohydride (40 mg in 0.5 mL DCM). After stirring for 4 h, 20 mg of PPh 4 BPh 4 was then added and dissolved in 0.5 mL of methanol. Stirring was continued for an additional 6 h. The resulting mixture was centrifuged at 10,000× g for 3 min to collect the supernatant. Dark yellow crystals were obtained by slow diffusion of diethyl ether into the supernatant over a period of two weeks. Synthesis of Cu 29 -2 The Cu 29 -2 nanocluster was synthesized according to ref. 67 . Cu(MeCN) 4 BF 4 (50 mg, 0.16 mmol) was dissolved in a mixed solvent of acetonitrile and chloroform. Under vigorous stirring, PPh 3 (50 mg, 0.19 mmol) and AdmSH (12 μL, 0.11 mmol) were successively added to this solution, followed by the addition of triethylamine (NEt 3 , 20 μL, 0.14 mmol). The solution was stirred for 20 min until it was clear. A methanol solution of the reducing agent NaBH 4 (50 mg, 1.32 mmol) was added all at once, resulting in immediate vigorous gas evolution. After stirring for 3 h, 10 mg of NaSbF 6 was added and dissolved in 0.5 mL of methanol. Stirring was continued for another 12 h. The resulting mixture was then centrifuged at 10,000 × g for 3 min, and an orange solid was collected as the main product. Chloroform (3 mL) was added to the solid product. The obtained orange solution was filtered and subjected to diethyl ether vapor diffusion. After standing at room temperature for two weeks, dark orange block-shaped crystals were obtained. Synthesis of Cu 14 -1 Cu(AdmCOO) 2 (42.2 mg, 0.10 mmol) was dissolved in a mixture of DCM and methanol (2 mL). To this solution, a DCM solution of AdmSH (17 mg, 0.1 mmol in 0.5 mL DCM) was added, followed by a solution of bis(triphenylphosphino)cuprous borohydride (40 mg in 0.5 mL DCM), under vigorous stirring. After stirring for 8 h, the resulting mixture was centrifuged at 10,000 × g for 3 min to collect the supernatant. Yellow crystals were obtained by slow diffusion of diethyl ether into the supernatant over a period of two weeks. Synthesis of Cu 14 -2 Cu 14 -2 was synthesized according to ref. 66 . Cu(PhCOO) 2 (42.2 mg, 0.10 mmol) and AdmSH (17 mg, 0.1 mmol) were dissolved in a mixed solvent of ethylene glycol and toluene at a molar ratio of 1:1. The mixture was heated at 80 °C for 48 h, resulting in a yellow solution. The solution was then carefully filtered and dried. DCM was added to the obtained solid, yielding a yellow solution. Yellow block crystals were obtained by vapor diffusion of diethyl ether into the solution. Synthesis of Cu 23 Cu(AdmCOO) 2 (42.2 mg, 0.10 mmol) was dissolved in a mixed solvent of DCM and methanol (2 mL). Under vigorous stirring, a DCM solution of C 12 H 10 S 2 (11 mg, 0.05 mmol in 0.5 mL DCM) was added to this solution, followed by a solution of bis(triphenylphosphine)copper(I) borohydride (40 mg in 0.5 mL DCM). After stirring for 5 h, 10 mg NaSbF 6 was added and dissolved in 0.5 mL of methanol. Stirring was continued for an additional 8 h. The resulting mixture was centrifuged at 10,000× g for 3 min to collect the supernatant. Grey-green crystals were obtained by slow diffusion of diethyl ether into the supernatant over a period of two weeks. Synthesis of Cu 16 Cu(BCPCOO) 2 (26 mg, 0.10 mmol) was dissolved in a mixture of DCM and methanol (2 mL). To this solution, a DCM solution of 4-fluorothiophenol (2.5 μL, 0.05 mmol in 0.5 mL DCM) was added, followed by a solution of bis(triphenylphosphino)cuprous borohydride (40 mg in 0.5 mL DCM), under vigorous stirring. After stirring for 8 h, the resulting mixture was centrifuged at 10,000× g for 3 min to collect the supernatant. Green crystals were obtained by slow diffusion of diethyl ether into the supernatant over a period of two weeks. Synthesis of Cu 50 -1, Cu 50 -2 and Cu 50 -3 Cu(BBC) 2 (53 mg, 0.12 mmol) was dissolved in a mixture of DCM and methanol (2 mL). To this solution, a DCM solution of 4-fluorothiophenol (5 μL, 0.04 mmol in 0.5 mL DCM) was added, followed by a solution of bis(triphenylphosphino)cuprous borohydride (40 mg in 0.5 mL DCM), under vigorous stirring. After stirring for 8 h, the resulting mixture was centrifuged at 10,000× g for 3 min to collect the supernatant. Red crystals were obtained by slow diffusion of diethyl ether into the supernatant over a period of two weeks. Cu 50 -2 (yellow crystals) and Cu 50 -3 (orange crystals) were synthesized similarly to Cu 50 -1, except Cu(PABA) 2 and Cu(TAA) 2 were used instead of Cu(BBC) 2 . Characterizations Electrospray ionization mass spectrometry (ESI-MS) Mass spectra were collected using an Agilent 6224 time-of-flight mass Spectrophotometer. The dilute sample solutions were passed over organic filters (pore diameter: 0.22 μm) in advance. The typical conditions for experiments were set as: capillary voltage: 4.0 kV, sample injection rate: 1.2 mL h −1 , drying gas temperature: 150 °C, nebulizer pressure: 0.2 MPa, and drying gas flow rate: 4 L h −1 . Energy-dispersive X-ray spectroscopy (EDS) EDS was recorded on Bruker XFlash6100 at room temperature. X-ray photoelectron spectroscopy (XPS) XPS spectral data for the Cu 36 H 8 cluster were collected on ESCALAB Xi+. All spectra were corrected with the C 1 s peak (284.5 eV). Thermogravimetric analysis (TGA) Thermogravimetric analysis was conducted utilizing the Libra TG209 device, with various heating protocols established for sample evaluation under a nitrogen atmosphere. Single crystal X-ray diffraction (SC-XRD) The diffraction data of the single crystals were collected on an Agilent Technologies SuperNova system X-ray single-crystal diffractometer using Cu K α ( λ = 1.54184 Å) at 100 K. The data were processed using CrysAlis Pro software. The structure was solved and refined using full-matrix least-squares based on F 2 using ShelXT 68 , ShelXL 69 in Olex2 70 . Nuclear magnetic resonance (NMR) 1 H, 2 H, 31 P, variable-temperature 1 H, and variable-temperature 1 H T 1 relaxation NMR spectra of the samples were collected at ambient conditions on a Bruker AV-600 spectrometer with solvent residual signal as an internal reference. All data were processed on MestReNova software. Transient absorption spectroscopy The fs-TA spectra were measured using a home-built femtosecond pump−probe set-up. The laser pulse (800 nm, 35 fs pulse width, 1 kHz repetition rate) was generated by a regeneratively amplified Ti: sapphire laser (Coherent Astrella-Tunalbe-USP, USA). The output of the pulse is then divided into two beams with a beam splitter. The 400 nm pump pulse was produced by doubling the 90% pulse of an 800 nm pulse with a beta barium borate crystal (type I, 0.5 mm thickness); the power of the pump pulse was about 0.2 μJ. The probe beam was delayed with a computer-controlled optical delay line and then focused on a thin sapphire plate to generate the white light supercontinuum, which was split into two beams by using a broadband 50/50 beam splitter as the signal and reference beams (450–800 nm). The focused pump and probe pulses overlapped in a sample cuvette or film sample. The mutual polarization between the pump and probe beams was set to the magic angle (54.7°) by placing a half-wave plate in the pump beam. There was no photodegradation after fs-TA experiments by checking the steady state absorption spectra. UV–Vis–NIR absorption spectroscopy UV – Vis – NIR spectra were collected by a JascoV-650 Spectrophotometer using a quartz cuvette of 1 mm path length. The signal from the blank solvent was subtracted. Computational details Electronic structure analysis of the Cu 36 H 8 nanocluster was conducted via DFT, maintaining crystallographic bond distances. Rotational studies of the individual adamantane groups were executed along the axis illustrated in Fig. 4d , with angular increments of 5° across the range of 0° to 180°. Excited state energies were obtained through sTDDFT 71 , 72 computations. Both DFT and sTDDFT calculations employed the hybrid B3LYP exchange-correlation functional in conjunction with a double-ζ (DZ) basis set 73 , 74 . A tighter convergence was achieved through setting the SCF convergence condition to 1 × 10 −8 , while the DIIS method was introduced to accelerate the SCF procedure via incorporating 12 expansion vectors. Scalar relativistic effects were accounted through the Zeroth-order regular approximation (ZORA) 75 , 76 . All computational calculations were performed using the Amsterdam Density Functional (ADF2021) software package 77 . Photothermal equipment Photothermal measurements were conducted using the LASEVER808HX-8W-FC laser and the LSR445SD-4.5W laser. The photothermal behavior of the sample was monitored by using the FOTRIC 246M-M50 infrared thermal imager test platform. Infrared photos and real-time temperatures were extracted from the video by AnalyzIR software. The illumination module featured a xenon lamp light source, a current regulator, a total reflection mirror, and an AM 1.5 filter to replicate the solar spectrum. Additionally, PCE calculations were performed as part of this study 78 , 79 . Based on the total energy balance for this system: ∑ i m i c p , i d T d t = Q s − Q loss 1 where m i (DMF: 0.474 g; DMSO: 0.55 g) and c p , i (DMF: 2.14 J g −1 °C −1 ; DMSO at 60 °C: 2.017 J g −1 °C −1 ; DMSO at 80 °C: 2.166 J g −1 °C −1 ) are the mass and heat capacity of system components, respectively. T is the system temperature, and t is time. Q s is the photothermal heat energy input by the laser (445 nm) to the sample. Q loss is thermal energy lost to the surroundings. When the temperature is maximum, the system is in balance, d T = 0 : Q s = Q loss = h S T − T surr = h S T max − T surr = h S Δ T max 2 where h is the heat transfer coefficient, S is the surface area of the container, T surr is the ambient temperature of the surroundings (≈22 °C), T max is the maximum system temperature and Δ T max is the maximum temperature change at the steady-state (plateau). (DMF at 0.5 W cm −2 and 1.0 W cm −2 : Δ T max are ≈ 37 °C and 59 °C; DMSO at 0.5 W cm −2 and 1.0 W cm −2 : Δ T max are ≈ 40 °C and 63 °C). The photothermal conversion efficiency η is calculated using Eq. ( 3 ), η = Q s Q I = h S T − T surr I 1 − 1 0 − A λ = h S Δ T max I 1 − 1 0 − A λ 3 where Q I is the photothermal energy absorbed by the sample when irradiated with laser (445 nm), I is the laser power (0.5 and 1.0 W cm −2 ) and A λ is the absorbance of the samples at the wavelength of λ (DMF: A 445 is 0.572; DMSO: A 445 is 0.510). To obtain the h S , the dimensionless driving force temperature θ (dimensionless) and sample system time constant τ s (s) are introduced as follows: θ = T − T surr T max − T max 4 τ s = ∑ i m i c p , i h S 5 Thus, d θ d T = 1 T max − T max d T d t = 1 Δ T max Q s − Q loss ∑ i m i c p , i = Q s − Q loss τ s h S Δ T max 6 d θ d T = Q s τ s h S Δ T max − Q loss τ s h S Δ T max = Q s τ s h S Δ T max − h S T − T surr τ s h S T max − T surr = Q s τ s h S Δ T max − θ τ s 7 When the laser is off (after the system reaches the maximum temperature), Q s = 0 . Therefore, d θ d T = − θ τ s 8 t = − τ s ln θ 9 To sum up, the value of τ s can be obtained from the slope of the cooling time vs. ln θ plot, and h S can be further derived. h S = ∑ i m i c p , i τ s 10 The method for measuring the solid-state PCE was described in the article 60 . The relevant calculation equations and parameters are as follows. Derivation of the heat dissipation coefficient H * of the sample from its thermal equilibrium state under electric heating. ∑ j Q j = m c p d T d t = P * − H * Δ T E , max 11 Δ T E , max = T E , max − T 0 12 P * = P un = S un S P 0 = r 2 r + 2 h P 0 13 where the energy term Q j includes the input and output energy to the sample, m and c p are the mass and heat capacity of the sample, respectively, T is the temperature of the sample, t is the measurement time. P * is the thermal power received by the sample, H * is the heat dissipation coefficient of the sample during electric heating. Δ T E , max is the maximum temperature change within the test area during electric heating. T E , max is the maximum temperature within the test area during electric heating, T 0 is the initial temperature of the system. P un is the output power of the resistor in the sample plane, S un represents the contact area between resistor and sample, S is the surface area of the resistor, P 0 is the input power of the resistor, r (2.5 mm) is the radius of the contact area, and h (0.8 mm) is the thickness of the resistor. When the temperature is maximum, the system is in balance, d T = 0 : P * − H * Δ T E , max = 0 14 Thus, H * = P * Δ T E , max 15 Similarly, under laser heating, the system reaches thermal equilibrium when d T = 0 , which is given as follows. ∑ j Q j = m c p d T d t = I 0 A λ η − H Δ T L , max = 0 16 Δ T L , max = T L , max − T 0 17 Thus, η = H Δ T L , max I 0 A λ 18 I 0 is the incident laser power, A λ is the absorbance of the samples at the wavelength of λ ( A 445 is 0.572;)., η is the solid-state PCE of the sample, Δ T L , max is the maximum temperature change within the test area during laser heating. T L , max is the maximum temperature within the test area during laser heating, T 0 is the initial temperature of the system., H is the heat dissipation coefficient of the test area during laser heating. Since the sample and substrate remain unchanged during laser heating and electric heating, the temperature-independent heat dissipation coefficients for laser heating ( H ) and electric heating ( H * ) are equal. H = H * 19 Therefore, η = H * Δ T L , max I 0 A λ 20 The relevant key parameters are listed below. The heat dissipation coefficient of the sample during electric heating, H * , was 0.00555. The temperature difference between the sample and its environment upon reaching thermal equilibrium under laser irradiation, Δ T L , max , was 7.01 K. The laser power, I 0 , was 0.117 W and the absorbance, A λ ( λ corresponds to 445 nm), was 0.429. Reporting summary Further information on research design is available in the Nature Portfolio Reporting Summary linked to this article. Supplementary information Supplementary Information (8MB, pdf) Reporting Summary (901.7KB, pdf) Transparent Peer Review file (6.7MB, pdf) Source data Source Data (41MB, zip) Acknowledgements H. Shen acknowledges the financial support from the National Natural Science Foundation of China (22301149 and 22571172), National Key R&D Program of China (2023YFB3507100), Natural Science Foundation of Inner Mongolia (2025JQ026), Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region (NJYT23035) and start-up funding of Inner Mongolia University (10000-23112101/043 and 23600-5233710). S. Li acknowledges the financial support from the National Natural Science Foundation of China (22565021), Natural Science Foundation of Inner Mongolia (2025QN02068), and Start-Up Funding of Inner Mongolia University (10000-A24202027). N.F. Zheng acknowledges the financial support from the National Natural Science Foundation of China (Grant no. 92261207) and the NSFC Center for Single-Atom Catalysis under grant no. 22388102) and the New Cornerstone Science Foundation. Q. Wu acknowledges the financial support from the National Natural Science Foundation of China (grant no. 22502162). D.S.N.D.S. and C. M. A. were supported by the National Science Foundation (CHE-2404212) of the United States. The computing for this work was performed on the Beocat Research Cluster at Kansas State University, which is funded in part by NSF grants CHE-1726332, CNS-1006860, EPS-1006860, and EPS-0919443. The variable-temperature 1 H NMR and variable-temperature T 1 relaxation NMR experiments were conducted at the NMR facility of the National Center for Protein Sciences at Peking University. We extend our sincere gratitude to Dr. Hongwei Li for his valuable guidance and support throughout the data acquisition and analysis process. We sincerely thank Professor Zhong Haizheng and Dr. Gu Kai from the School of Materials Science and Engineering at Beijing Institute of Technology for their invaluable assistance in the measurement and analysis of solid-state photothermal conversion efficiency. We also extend our heartfelt gratitude to Mr. Xu Hao from the Innovation Laboratory for Sciences and Technologies of Energy Materials of Fujian Province for his invaluable support in the measurement and analysis of solid-state variable-temperature nuclear magnetic resonance. Author contributions B.Y. and H.S. designed the research. B.Y. did most of the experiments. B.Y., J.S., H.D., L.L., M.Q., F.Z., Q.X., H.G., X.S., X.G., R.H., M.Z., Q.W., Z.X., C.X., Y.W., X.J., S.L., F.L., and M.Z. performed the sample characterization. B.Y., J.S., D.S.N.D.S., C.M.A., N.Z., and H.S. wrote the paper. B.Y., J.S., D.S.N.D.S., analyzed the data. N.Z. and H.S. secured the funding required for the project. C.M.A., N.Z., and H.S supervised the overall study. H.S. reviewed the manuscript. All authors participated in the discussions regarding the research progress and results. B.Y., J.S., D.S.N.D.S. contributed equally to this work. Peer review Peer review information Nature Communications thanks Sheshanath Bhosale, and the other anonymous reviewers for their contribution to the peer review of this work. A peer review file is available. Data availability The data that support the findings of this study are available from the corresponding authors upon request. X-ray crystallographic structures reported in this work have been deposited at the Cambridge Crystallographic Data Center (CCDC) under deposition numbers 2421047, 2522686, 2522682, 2522675, 2522681, 2522680, 2522696, 2522697, 2522699. Source data are provided with this paper. Competing interests The authors declare no competing interests. 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Supplementary Materials Supplementary Information (8MB, pdf) Reporting Summary (901.7KB, pdf) Transparent Peer Review file (6.7MB, pdf) Source Data (41MB, zip) Data Availability Statement The data that support the findings of this study are available from the corresponding authors upon request. X-ray crystallographic structures reported in this work have been deposited at the Cambridge Crystallographic Data Center (CCDC) under deposition numbers 2421047, 2522686, 2522682, 2522675, 2522681, 2522680, 2522696, 2522697, 2522699. Source data are provided with this paper. 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