Rational cyano functionalization of copper phenylacetylide paves the way for superior photogenerated electron transport capability and diclofenac degradation

Abstract

Photocatalytic technology is a promising solution for effectively removing diclofenac (DCF) from wastewater. Herein, we report the theoretical design and solvothermal synthesis of a cyano-modified copper phenylacetylide (PhC₂Cu) photocatalyst (Cy–PhC₂Cu), addressing the bottleneck of rapid charge carrier recombination in pristine PhC₂Cu. The strong electron-withdrawing nature of cyano (–CN) not only facilitates photogenerated electron transfer on copper(I) sites and induces oxygen activation, but also lowers the valence band (VB) energy level, thereby promoting the generation of highly oxidizing holes (h⁺) to enhance the production of ¹O₂. Characterization experiments confirm that doping of –CN exhibits a broadened light absorption range and superior photocatalytic activity toward DCF degradation under visible light. Specifically, Cy–PhC₂Cu achieved a 97.0% DCF degradation rate within 100 min, which is 5.99 times higher in kinetics than pure PhC₂Cu. In the photocatalytic process, electrons are excited by copper(I) and enter the benzene ring ligand through alkynyl groups. The presence of electron-deficient –CN can further capture these electrons, avoiding their rapid return to copper under strong Coulomb forces within the molecule, resulting in effective exciton separation, which was confirmed by the combined results of photoluminescence (PL) spectra and density functional theory (DFT) calculations. This work demonstrates that rational functional group engineering paves the way for designing advanced photocatalysts with optimized optoelectronic transport for water treatment applications.