Substituent engineering of edge-modified cobalt polyphthalocyanine for optimizing near-infrared photocatalytic imines synthesis: dual regulation of surface catalytic reactions

The photocatalytic oxidative coupling of amines has emerged as a promising alternative for imine production. Nevertheless, enhancing the photocatalytic activity of conjugated organic polymers (COP) still faces significant challenges, particularly in near-infrared (NIR) driven photocatalytic activity, charge separation efficiency, adsorption, and activation of amine molecules. Here, we tackled these challenges by modulating the internal electronic states of cobalt phthalocyanine polymers (C-CoPPc-x) through edge-substituted modification with various electron-donating or electron-withdrawing groups. The built-in electric field (B-IEF) and Lewis acidity of metal sites are significantly influenced by such an edge-substituted modification, which further results in an adjustable separation efficiency of photogenerated charges and the adsorption/activation behavior of benzylamine. By optimizing the surface catalytic reactions of COP, the methoxy-edge-modified polymer demonstrated a superior performance with an amine yield of 4.32 mmol g⁻¹ under NIR irradiation, surpassing the performance of many reported photocatalysts even under ultraviolet (UV) or visible light. This work underscores the substantial impact of minor substituent modifications on both the separation of photogenerated charge carriers and the adsorption/activation of amine molecules in the photocatalytic process, and provides valuable insights for enhancing the photocatalytic performance of COP in diverse applications.