Highly Selective CO2 Electroreduction to C2H4 Using a Metal-Organic Framework with Dual Active Sites

Conversion from CO2 to C2H4 is important for the development of energy and the environment, but the high energy barrier of hydrogenation of the *CO intermediate and C-C coupling step tend to result in C-1 compounds as the main product and thus restrict the generation of C-2 H-4. Here, we report a metal-organic framework (denoted as PcCu-Cu-O), composed of 2,3,9,10,16,17,23,24-octahydroxyphthalo-cyaninato)copper(II) (PcCu-(OH)(8)) ligands and the square-planar CuO4 nodes, as the electrocatalyst for CO2 to C2H4. Compared with the discrete molecular copper-phthalocyanine (Faradaic efficiency (FE) of C2H4 = 25%), PcCu-Cu-O exhibits much higher performance for electrocatalytic reduction of CO2 to C2H4 with a FE of 50(1)% and a current density of 7.3 mA cm(-2) at the potential of -1.2 V vs RHE in 0.1 M KHCO3 solution, representing the best performance reported to date. In-situ infrared spectroscopy and control experiments suggested that the enhanced electrochemical performance may be ascribed to the synergistic effect between the CuPc unit and the CuO4 unit, namely the CO on the CO-producing site (CuO4 site) can efficiently migrate and dimerize with the *CO intermediate adsorbed on the C-2 H-4-producing site (CuPc), giving a lower C-C dimerization energy barrier.

Automated summary

In this study, a metal-organic framework (PcCu-Cu-O) was reported as an electrocatalyst for converting CO2 to C2H4, showing higher efficiency compared to discrete molecular copper-phthalocyanine. In-situ infrared spectroscopy and control experiments indicated that the synergistic effect between the CuPc unit and the CuO4 unit contributes to lowering the energy barrier for C-C dimerization.