Abstract
Heterogenized cobalt phthalocyanine (hetero-CoPc) molecular catalysts exhibit domino CO/methanol selectivity during CO(2) electroreduction. However, the origin of this selectivity is not well understood, impeding the strategic optimization for methanol generation. Here, we show potential-modulated orbital interaction mechanisms governing the selectivity in hetero-CoPc based on first-principles calculations with consideration of carbon support and electrochemical interfaces. Specifically, constant-potential orbital-resolved analyses reveal that electrons introduced by applied potentials initially occupy the semi-occupied Co-3d(z)((2)) orbital, thus suppressing CO-5σ → Co-3d(z)((2)) electron donation. This induces gradual weakening of *CO adsorption while establishing high *CO hydrogenation barriers (restricting the product to CO) over the medium potential range. With further decreasing potentials, a progressive electron population occurs in the Co-3d(yz)/d(xz) orbitals, promoting the Co-3d(xz)/d(yz) → CO-2π* back-donation. This facilitates the activation of the C─O bond of *CO, thereby reducing its hydrogenation barriers and enabling methanol production at more negative potentials. Similar analyses also rationalize experimental observations for other heterogenized metal phthalocyanines, showing the importance of potential-modulated orbital interactions for selectivity engineering.