Steering Cu Interatomic Distances and Local Steric Environment of Nonporous Coordination Polymers Boosts CO2 Electroreduction to C2 Products.

Metal-organic frameworks (MOFs) and porous coordination polymers (CPs) are promising electrocatalysts for CO2 reduction, but suffer from poor stability and mass transfer limitations at high current densities. While nonporous CPs show efficient CO2-to-C1 conversion with exceptional stability, their application for C2 synthesis remains unexplored. Herein, we report the first rational design of nonporous CPs for efficient CO2-to-C2 conversion. Two structurally related nonporous CPs (Cuptz-1 and Cuptz-2) are constructed from an identical pyridyl tetrazole ligand and different copper precursors, with distinct Cu interatomic distances and local steric environments. With shorter Cu interatomic distances and local steric confinement, Cuptz-1 outperforms Cuptz-2, reaching 74.4% C2 Faradaic efficiency and a partial current density of 310.2 mA cm-2, both values among the highest reported. Notably, Cuptz-1 retains stable performance for over 25 h at 100 mA cm-2, whereas Cuptz-2 exhibits a slight potential drift after 15 h. Mechanistic studies reveal that the shorter Cu interatomic distances and steric confinement in Cuptz-1 create a short reaction path for C-C coupling intermediates via monodentate adsorption and direct adjacent proton transfer, resulting in a significantly lower rate-determining step barrier than the bidentate adsorption-induced long reaction path on Cuptz-2.