Mixed-valence Cu-based metal-organic framework for selective CO2 electroreduction to C1 liquid fuels with high energy conversion efficiency

Efficient CO2 electroreduction requires catalysts for enhanced energy conversion efficiency and carbon product selectivity with low overpotential, in consideration of the interference of competitive H2 evolution reaction and complex intermediate species involved. We proposed that adaptive electronic structures based on dynamic mixed-valence interconversion would facilitate electron transfer and intermediate turnover during the catalysis, ensuring high activity, selectivity, and durability. Herein, a novel mixed-valence Cu-based metal-organic framework was prepared using an electron-rich linker for electrocatalytic reduction of CO2. The designed material delivered a remarkable Faradaic efficiency of 99.2% for C1 liquid fuels at a low reduction potential of -0.1 V versus reversible hydrogen electrode, considerably higher than that of the commercial copper foam and competitive to the Cu-based electrocatalysts reported. The experimental data and theoretical calculations verified the Cu(I)/Cu(II) interconversion and the much higher energy barrier of H2 evolution than carbon product generation. Such a feasible strategy, simultaneously improving energy conversion efficiency, carbon product selectivity, and structural robustness, provides great insights into rational catalyst customization for sustainable CO2 conversion.