关键词: 纳米团簇, 钛, 锆, 深共熔溶剂热, 产氢

Abstract:

Atomically precise nanoclusters form an important class of functional materials that have recently attracted research interest for their unique properties and easily tunable surface functionalities. Core-shell nanomaterials with precise structural information can be produced to better understand the structure–property relationships for different applications. Polyoxo-titanium clusters (PTCs) are such a kind of nanomaterial for different functional applications in catalysis, photovoltaics, ceramics, etc. However, the high bandgap of semiconductive PTCs is the limiting factor in their practical solar application in the visible region of sunlight. The development of PTCs with different surface-bound ligands is an emerging area of research in the design and synthesis of core-shell nanoclusters with reduced bandgaps. It has been extensively reported that the polynuclear growth of PTCs requires molecular-level water supply in reactions. Moreover, it is important to identify more environment-friendly synthetic methods. Deep eutectic-solvothermal (DES) synthesis is an emerging green method for the synthesis of different crystalline materials. The hygroscopic nature of DES should enhance the provision of water during polynuclear growth of nanoclusters. Hence, we chose to synthesize different kinds of PTCs using DES as solvent. Two nanoclusters, Zr-oxo (PTC-65) and Zr/Ti-oxo (PTC-66) clusters having surface-bound 1, 10-phenanthroline (1, 10-phn) and phenol ligands, were successfully synthesized using this approach; 1, 10-phn was employed as the precursor in the synthetic reaction, and phenol was not employed directly in the chemical reaction, but was supplied from the DES solvent used in the reaction. In the presence of chromophoric ligands, 1, 10-phn and phenol are believed to enhance the light absorption properties of the resulting functional nanomaterials. Their crystal structure revealed that they form core-shell mimics with Zr-oxo and Ti/Zr-oxo core units having surface-bound shell ligands. Based on their different structural characteristics, photocatalytic hydrogen evolution studies were performed on these two functional materials using an aqueous solution of H₂O (50 mL)/triethanol amine (10 mL). Interestingly, PTC-65 formed a turbid solution, whereas PTC-66 formed a clear solution. The possible reasons for their different dispersion behaviors are widely discussed, with emphasis on their structure–property relationships. This study provides a potential tool for the homogenization of Ti-O materials to improve their photocatalytic activities. Moreover, the success of our work confirms that deep eutectic-solvothermal synthesis can be an effective method for cluster preparation. Many other interesting polynuclear complexes like polyoxometalates, chalcogenides, and noble-metal clusters could be obtained by this synthetic methodology.

Key words: Nanocluster, Titanium, Zirconium, Deep-eutectic solvothermal, H₂ evolution