Regulating Spin Density using TEMPOL Molecules for Enhanced CO 2 ‐to‐Ethylene Conversion by HKUST‐1 Framework Derived Electrocatalysts

Abstract The selectivity of multicarbon products in the CO 2 reduction reaction (CO 2 RR) depends on the spin alignment of neighboring active sites, which requires a spin catalyst that facilitates electron transfer with antiparallel spins for enhanced C−C coupling. Here, we design a radical‐contained spin catalyst (TEMPOL@HKUST‐1) to enhance CO 2 ‐to‐ethylene conversion, in which spin‐disordered (SDO) and spin‐ordered (SO) phases co‐exist to construct an asymmetric spin configuration of neighboring active sites. The replacement of axially coordinated H 2 O molecules with TEMPOL radicals introduces spin‐spin interactions among the Cu(II) centers to form localized SO phases within the original H 2 O‐mediated SDO phases. Therefore, TEMPOL@HKUST‐1 derived catalyst exhibited an approximately two‐fold enhancement in ethylene selectivity during the CO 2 RR at −1.8 V versus Ag/AgCl compared to pristine HKUST‐1. In situ ATR‐SEIRAS spectra indicate that the spin configuration at asymmetric SO/SDO sites significantly reduces the kinetic barrier for *CO intermediate dimerization toward the ethylene product. The performance of the spin catalyst is further improved by spin alignment under a magnetic field, resulting in a maximum ethylene selectivity of more than 50 %. The exploration of the spin‐polarized kinetics of the CO 2 RR provides a promising path for the development of novel spin electrocatalysts with superior performance.