Coordination-tailored conductive metal-organic frameworks boost CO₂ electroreduction to ethylene for cascade ethylene...

The electrochemical conversion of CO₂ to ethylene glycol (EG) represents a sustainable pathway, reducing dependence on fossil fuels while avoiding CO₂ emissions. Effectively regulating ethylene formation is essential for the successful electrosynthesis of EG from CO₂. Herein, we propose a d-orbital energy level regulating strategy to form the highest occupied-orbital of Cu center in the conductive metal-organic frameworks (cMOFs) for efficient CO₂RR towards C₂H₄. Three 2D copper-based cMOFs with square-planar nodes Cu-N₂O₂, CuN₄, CuO₄ are constructed to tune the C₂H₄ production. Different from the Cu-THQ (THQ: tetrahydroxy-1,4-quinone) with Cu-O₄ motifs that primarily generate CO and the metastable Cu-HAB (HAB: hexaaminobenzene) with Cu-N₄ nodes derived Cu nanoparticles to favor HCOOH formation, the Cu-TABTO (TABTO: 1,3,5-triamino-2,4,6-benzenetriol) with Cu-N₂O₂ coordination mode shifts the primary product to C₂H₄, achieving the C₂H₄ Faradaic efficiency of 50.7% and an impressive total current density of 460.7 mA cm^-2. Theoretical calculations reveal that the asymmetric N,O-coordination mode induces the 3d_xz as the highest occupied orbital of Cu in Cu-TABTO, facilitating the formation of 3d_xz-π* bonds, thereby enhancing the adsorption of *CO and lowering the energy barrier for C-C coupling. We further cascade the electrocatalytic CO₂-C₂H₄ system with titanium silicalite-1 (TS-1)/H₂O₂ system to demonstrate the high potential to transfer the obtained C₂H₄ into ethylene glycol with the yield of 902.4 μmol L^-1. This work demonstrates the importance of precisely controlling C₂H₄ generation via coordination-atom-directed orbital energy distribution in cMOFs, while simultaneously establishing the viability of electrocatalytic conversion CO₂ to ethylene and finally to realize efficient EG production via a cascade system.