Trinuclear copper clusters in three-dimensional covalent organic framework for enhanced electroreduction of carbon dioxide to ethylene

Confining Cu clusters into covalent organic frameworks (COFs) has been revealed to be an effective strategy to enhance the stability of Cu clusters for the electrocatalytic conversion of carbon dioxide (CO₂) to ethylene (C 2 H 4 ). However, this strategy still exhibits unsatisfactory selectivity and efficiency. Herein, the reaction of a trinuclear Cu-cluster-based building unit, tris(4-μ 2 -O-carboxaldehyde-pyrazolato-N, N′)-tricopper (Cu 3 ), with a 4-connected square-planar linker of 4,4′,4”″,4″′-(pyrene-1,3,6,8-tetrayl)tetraaniline (Py) afforded a trinuclear Cu-cluster-containing three-dimensional (3D) COF, named 3D-Cu 3 -Py-COF. Powder X-ray diffraction combined with theoretical simulations reveals the crystalline nature of 3D-Cu 3 -Py-COF with a tbo topology. Comparative studies demonstrate that the 3D framework of 3D-Cu 3 -Py-COF enhances the exposure of active sites and improves CO 2 adsorption capacity. This, in cooperation with the capacity of trinuclear Cu-cluster moieties to facilitate C C coupling, endows 3D-Cu 3 -Py-COF with excellent electrocatalytic performance and selectivity for CO₂ reduction reaction (CO₂RR) to C 2 H 4 , exhibiting a maximal Faraday efficiency of 44.6% for C 2 H 4 at −0.8 V vs. reversible hydrogen electrode. This work should be helpful for the strategic design and fabrication of efficient Cu-cluster-based electrocatalysts for promoting the conversion of CO₂ into valuable carbon-based fuels.