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

Copper-coordinated catalysts are reported to be effective for electrocatalytic CO 2 reduction reaction (CO 2 RR) 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 CO 2 RR 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 CO 2 RR 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 CO 2 RR with high selectivity toward C 2 products.