Polydopamine Coating of a Metal–Organic Framework with Bi-Copper Sites for Highly Selective Electroreduction of CO2 to C2+ Products

Abstract

Conversion from CO2 to the more desirable and valuable C2+ products under neutral conditions is important for the development of energy and the environment, but it is a challenging work. In this work, we demonstrate that the bi-copper sites on the crystal surface of a metal–organic framework Cu-HITP (HITP = 2,3,6,7,10,11-hexaiminotriphenylene) are very suitable for catalyzing the low-energy pathway of *CO coupling with *COH to form *OCCOH. The in situ infrared spectroscopy, theoretic calculations, and controlled experiments show that polydopamine coating of Cu-HITP could provide a carbon dioxide reduction reaction-favored local environment with proton sources and hydrogen-bond donors around the bi-copper active sites to promote *CO hydrogenation and stabilize the key intermediates (*COH and *OCCOH), resulting in a high selectivity of the C2+ reduced products [Faradaic efficiency (C2+) of 75(3)%, Faradaic efficiency (C2H4) of 51(1)%] in the KHCO3 electrolyte. This work provides an insight into the catalytic activity on the surface of metal–organic frameworks and the local environment for electroreduction of CO2 to C2+ products.