Concave and Convex Molecular Curvature Modulates Spatial Electronic Environments for Controlled Electrocatalysis.

Molecular catalysts offer well-defined active sites and tailorable structures that together govern their intrinsic activity. While molecular curvature has emerged as a powerful tool for modulating catalytic activity, the role of the local curvature environment remains poorly understood. Here, we demonstrate that the catalytic properties of iron phthalocyanines (FePc) are strongly influenced by the spatial concave and convex architectures. Although FePc has been predominantly reported to catalyze four-electron O2 reduction, reports of its two-electron pathway are rare. By depositing FePc on carbon supports with a cylindrical mesopore (concave-FePc) and its inverse architecture (convex-FePc), we demonstrate that convex-FePc preferentially catalyzes the four-electron O2 reduction route, whereas concave-FePc favors the two-electron pathway, primarily producing H2O2 with selectivity exceeding 80%. In situ electrochemical infrared spectroscopy and theoretical calculations reveal that local concave/convex geometries of FePc modulate the electronic properties of the Fe site and its interaction with key intermediates via spatial orbital rearrangement. Specifically, the confined environment under the concave curvature reduces orbital overlaps between Fe dz2 of FePc and O p of *OOH, thereby weakening *OOH adsorption and boosting O2-to-H2O2 conversion. This curvature-dependent activity also extends to CoPc/MnPc and electrochemical CO2 reduction, underscoring the versatility of this approach. Our findings present a general design framework for engineering the catalytic performance of molecular catalysts through a tailored curvature environment.