σ-π dative bond stabilizing copper active site drives CO2 electrocatalysis to hydrocarbon.

Copper-based catalysts are the premier choice for electrochemical reduction of CO2 (CO2RR) into hydrocarbons or oxygenates. However, the facilely structural reconstruction of copper sites during electrolysis poses significant challenges to the long-life electrolytic efficiency. Herein, we leverage the strong σ-π dative bonding between Cuδ+ and alkyne-based ligands to stabilize copper sites for the prolonged CO2RR. We demonstrate the feasibility of taming the electronic structures of copper sites through the tug of war between σ and π backbonding interactions. The optimal copper organic polymer with methoxy group functionalization (OMe-PhCu) exhibits a moderate charge density of copper sites and an intensified local asymmetric charge distribution of coordinative carbon, enhancing the selectivity of methane with a Faradaic efficiency of 68.8% and a partial current density of 324.5 mA cm-2 in acidic electrolyte. In situ spectra and density functional theory calculations reveal enhanced *CO adsorption and lowered energy barrier for CO2RR into methane over OMe-PhCu. Building upon such stable Cuδ+ sites, we further construct Cuδ+/Cu0 catalytic interfaces for the generally enhanced electrosynthesis of multi-carbons and ammonias. This synthetic chemistry paves the pathway for the design of stable catalytic active sites for renewable conversions.