Spatially Decoupling Co–Ni Centers beyond Sub-Nanometer Distances Enable Auto-Relay Catalysis for C–H Bond Oxidation

Cooperative catalysis typically requires bimetallic centers to be positioned at sub-nanometer distances to enable electron coupling. However, auto-relay catalysis, wherein multiple catalytic cycles with distinct functions operate synergistically within the same catalytic system, has rarely been systematically studied from the perspective of intermetallic distances. This work presents an auto-relay catalytic system based on spatially decoupled dual metal sites anchored within a porphyrin-based porous aromatic framework (Por-PAF) for efficient hydrocarbon oxidation. The Por-PAF(Co&Ni)-2 exhibits an amorphous microporous/mesoporous composite structure, good thermal stability, and highly dispersed Co2+ and Ni2+ catalytic centers with an average intermetallic distance of 2.55 nm. Cyclohexane is selected as a model substrate to evaluate the catalytic performance of Por-PAF(Co&Ni)-2 in C-H bond oxidation. The cyclohexane conversion is 7.1% with the selectivity toward partial oxidation products (cyclohexanol, cyclohexanone, and cyclohexyl hydroperoxide) of 85.9%, delivering a high turnover number (TON) of 13,826 and turnover frequency (TOF) of 1728 h-1. Kinetic analysis indicates that apparent activation energy (Ea) is reduced to 92.69 kJ·mol-1, and activation entropy (ΔS‡) is -134.2 J·mol-1·K-1, reflecting an ordered transition state jointly induced by nanoconfinement effect and the spatial decoupled bimetallic centers. Mechanistic studies support an auto-relay catalysis mechanism, in which the cobalt center activates O2 and governs the hydroxyl rebound pathway, whilst the nickel center captures peroxides derived from escaped radicals, thereby further driving C-H bond oxidation. This catalytic system also exhibits good substrate universality. This study fills a critical gap in the research on bimetallic distance in auto-relay catalysis and provides new insights for the rational design of highly selective C-H bond oxidation.