Coupled Spin and Charge Transfer in Molecular Magnet Crystals for Enhanced Hydrogen Evolution

Although spin states are known to influence conductivity and coordination environments, their modulation has rarely been employed to optimize the hydrogen evolution reaction (HER) performance, owing to the nonmetallic nature of typical active sites. Here, density functional theory calculations on two-dimensional TM 2 (TCNQ) 2 (TM = Cr, Mn, Fe, Co, Ni; TCNQ = tetracyanoquinodimethane) lattices reveal that single-molecule magnets (Cr, Mn, Fe) can act as charge-spin-coupled catalysts, where charge transfer (Δ e ) and magnetic moment variation (Δ M ) are interdependent and mediated by neighboring TM atoms. A linear Δ M T –Δ e correlation underscores this coupling, with HER activity enhanced as Δ M TM-II decreases. In contrast, for Co and Ni, the C3 site, located at the vertex of the six-membered ring, emerges as the optimal catalytic center, where adsorption induces local reconstruction and spin quenching or even demagnetization yet with negligible charge redistribution. These findings offer a fresh perspective on spin-polarized catalysis and broaden the design principles of metal–nitrogen–carbon systems for HER active sites.