Assembly of High-Nuclearity Copper(I) Alkynyl Nanoclusters with Exposed Polyoxomolybdate Templates

The directed synthesis of copper(I) nanoclusters with atomically precise active sites for photocatalytic CO₂ reduction reaction (CO₂RR) poses notable challenges. By carefully regulating the acidity of the reaction system, a set of five atomically precise Mo-Cu heterometallic nanoclusters were effectively synthesized. The adjustment of the reaction system's acidity stimulates the polymerization of molybdate, consequently influencing the encapsulation structure of the outer copper(I) shell and thereby controlling the number of catalytically active sites located at the periphery of these nanoclusters. When subjected to xenon lamp irradiation, the synthesized Mo-Cu nanoclusters, which showcase exposed polyoxomolybdates, exhibit significantly activity in the conversion of CO₂ to CO (up to 160.8 µmol g^-1 h^-1) while maintaining an impressive selectivity of up to 99.9% without any additional sacrificial agent, cocatalyst or photosensitizer. When sacrificial agent and photosensitizer were added to the CO₂RR system, the maximum CO production rates for Mo₁₆Cu₃₆-1 and Mo₂₂Cu₃₀ were 5672.1 µmol g^-1 h^-1 and 7370.8 µmol g^-1 h^-1, respectively, with CO selectivities of 90.3% and 90.6%. The Mo─O─Cu active sites play a dual role in enhancing both CO₂ adsorption and activation, as well as facilitating charge separation. This study not only elucidates the synthesis of high-nuclearity Mo-Cu nanoclusters with potent photocatalytic activity in CO₂RR but also contributes to advancing our comprehension of the structure-property relationship inherent in nanocluster photocatalysts.