Boosting cumene hydrogen transfer via a Ru-based porphyrin covalent organic framework for tandem air epoxidation of olefins

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Constructing catalysts featuring an ordered structure, stable performance and uniformly dispersed catalytic sites is vital for the epoxidation of small-molecular olefins. Here, we design catalysts by tracing the oxidation-process origin and synthesize a series of highly dispersed metal porphyrin-based covalent organic framework materials (COFs). The aim is to efficiently oxidize the C-H bonds of cumene by air to in-situ generate organic peroxides at a safe concentration, and integrate the multi-step oxidation method of cumene in industry into a one-step method for olefins' epoxidation. The carbonyl-ruthenium COF (Ru-COF-1) exhibits excellent performance, with 98% epoxide selectivity, 1221.77 h⁻¹ productivity, and over 95% selectivity after 9 cycles for 1-hexene. Analysis of structure-properties-catalytic relationships of Ru-COF-1 shows that, compared with Ru-porphyrins and metal-free COFs, the enhanced reaction performance mainly results from Ru metal introduction, which promotes benzylic proton transfer in cumene. Besides, Ru-COF-1’s porous, ordered structure aids oxygen enrichment, forming active peroxy radicals with the cumene carbon-centered radicals formed on the catalyst surface. Ru-H sites then accelerate active oxygen transfer from peroxy radicals, enabling olefin tandem epoxidation. DFT calculations verify the reaction mechanism, and this work offers a reference for the design of catalysts for the green, safe and efficient oxidation of olefins.