New Strategy for Cluster-Based Covalent Organic Framework: Thermally Induced Covalent Crosslinking of Highly Stable...

Copper nanoclusters (Cu NCs) have emerged as a remarkable class of CO₂ reduction reaction catalysts that are distinguished by their unparalleled reactivity, but effectively modulating the transport pathway of charge carriers between Cu NCs by feasible chemical means is still challenging. Herein, a thermally induced covalent crosslinking strategy is proposed to modulate the fast electron transport pathway formed between clusters. A copper-sulfur-nitrogen cluster [Cu₄(SN)₄] (denoted Cu₄SN) is first synthesized; subsequently, the SN ligands in Cu₄SN are coupled covalently via a thermally induced covalent crosslinking strategy to yield CC-Cu₄SN, which exhibits enhanced conductivity and photocarrier transport. As expected, CC-Cu₄SN shows a high photocatalytic CO production rate of 29.98 µmol g^-1 h^-1 with ≈99.5% selectivity in CO₂ reduction with H₂O as sacrificial agents, which is more than 10 times superior to that observed with Cu₄SN. Systematic experiments and density functional theory calculations reveal that the covalent crosslinks between clusters accelerate the dynamic transfer of photoexcited charge carriers, increase the light utilization ability, favor CO₂ adsorption and ^*COOH generation, thereby accounting for the increased CO₂ photoreduction activity. This work presents a novel thermally induced internal covalent crosslinking strategy for synthesizing novel cluster-based covalent polymers with enhanced stability and catalytic activity.