Control of evolution of porous copper-based metal-organic materials for electroreduction of CO₂ to multi-carbon products

Electrochemcial reduction of CO₂ to multi-carbon (C2+) 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 C₂₊ products with a total current density of 268 mA/cm2 and Faradaic efficiency of 37% for electrochemcial reduction of CO₂ in 1 M aqueous KOH electrolyte at −2.27 V vs RHE (reversible hydrogen electrode). In situ 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 CO₂ to C₂₊ products.