Cationic covalent framework microenvironment steering CuPt alloy toward record-breaking photoelectrochemical ethane synthesis from CO2

Abstract

Photoelectrochemical CO₂ reduction to multi-carbon products fuels remains challenged by inefficient C–C coupling and competing proton reduction reaction. Herein, we designed a cationic covalent organic framework (COF⁺) to create an electrostatic microenvironment that synergizes with CuPt alloy nanoparticles for selective ethylene/ethane production. By spatially decoupling CO₂ enrichment from proton exclusion, the COF⁺/CuPt interface simultaneously facilitates CO₂ accessibility while impeding H⁺ migration, suppressing the hydrogen evolution reaction (HER). This unique microenvironment stabilizes key anionic intermediates (*COO⁻, *OCCO⁻) and promotes *CO dimerization, steering electron transfer toward C–C coupling. The optimized system achieves a record-high Faradaic efficiency of 51.5 %±5.3 % for ethane and 10.6 %±2.5 % for ethylene with a total C₂⁺ yield exceeding 62 % at −0.25 V vs. RHE and high stability (>300 min), representing the highest performance for photoelectrochemical CO₂ reduction to ethane. The combined analyses of in situ spectroscopy and theoretical calculations reveal that electrostatic field effects lower the energy barrier for *OCCO formation while accelerating hydrogenation kinetics. Therefore, this work demonstrates that microenvironment modification of the active site by cationic covalent organic framework is a versatile strategy for solar-driven CO₂ conversion into value-added hydrocarbons.