Tuning d-Band Structure of Cu-II in Coordinated Polymer via d-pi Conjugation for Improving CO2 Electroreduction Selectivity toward C-2 Products

Copper-coordinated catalysts are reported to be effective for electrocatalytic CO2 reduction reaction (CO2RR) to C-2 products but suffer from low selectivity. Herein a strategy was developed to tune the d-band structure of Cu-II via coordinating with aromatic ligands to form Cu-based conjugated polymers for CO2RR to C-2 chemicals. The catalysts derived from copper chloride coordinating with tetraminobenzoquinone (TABQ) and with 1,2,4,5-benzenetetramine possessed high-density and compact Cu single-atom sites and displayed high activity for CO2RR to C-2 products. Especially, Cu-TABQ exhibited a maximum C-2 faradaic efficiency of 63.2 % with a current density of 423 mA cm(-2) at -1.17 V (vs. reversible hydrogen electrode). Density functional theory calculations indicated that the TABQ linker possessing C=O groups significantly widened the d-band of coordinated Cu-II, which facilitated binding of *CO intermediate on the catalyst and thus enhanced C-C coupling. This work provides mechanistic insight into the Cu-II-coordinated polymers for CO2RR with high selectivity toward C-2 products.