Control of evolution of porous copper-based metal-organic materials for electroreduction of CO to multi-carbon products.

Electrochemcial reduction of CO to multi-carbon (C) products is an important but challenging task. Here, we report the control of structural evolution of two porous Cu(ii)-based materials (HKUST-1 and CuMOP, MOP = metal-organic polyhedra) under electrochemical conditions by adsorption of 7,7,8,8-tetracyanoquinodimethane (TNCQ) as an additional electron acceptor. The formation of Cu(i) and Cu(0) species during the structural evolution has been confirmed and analysed by powder X-ray diffraction, and by EPR, Raman, XPS, IR and UV-vis spectroscopies. An electrode decorated with evolved TCNQ@CuMOP shows a selectivity of 68% for C products with a total current density of 268 mA cm and faradaic efficiency of 37% for electrochemcial reduction of CO in 1 M aqueous KOH electrolyte at -2.27 V RHE (reversible hydrogen electrode). electron paramagnetic resonance spectroscopy reveals the presence of carbon-centred radicals as key reaction intermediates. This study demonstrates the positive impact of additional electron acceptors on the structural evolution of Cu(ii)-based porous materials to promote the electroreduction of CO to C products.