Subangstrom spatial regulation of Fe1-N4 coordination structure for remarkably efficient C−H bond oxidation

Abstract

Structural regulation of heterogeneous active centers has been widely explored at the nano- and atomic-level, yet achieving subangstrom precision remains highly challenging. Here, we demonstrate subangstrom spatial regulation of the Fe−N bond within a fully uniform Fe₁-N₄ coordination structure. Strikingly, a 0.1 Å bond compression led to nearly a 23-fold enhancement in C−H bond oxidation. Advanced characterizations confirmed the uniform low-spin Fe₁-N₄ configuration, with the Fe−N bond distance gradually decreasing from 2.03 to 1.93 Å during pyrolysis. This subtle structural modification originates from the concerted effect of temperature- and curvature-induced distortion on the curved carbon surface, as further supported by theoretical simulations. The Fe−N bond distance was found to govern the electronic structure of the Fe center, where compressed coordination promotes electron accumulation. This structural modulation directly results in the high capability for peroxide group activation on Fe₁ single atoms, which affords outstanding C−H bond oxidation, comparable to supported noble metal catalysts. This study provides the experimental demonstration of structural regulation at subangstrom scale, extending the concept of “precise chemistry” in catalyst design from the nano- and atomic- to the subangstrom scale.