Identification of key oxidative intermediates and the function of chromium dopants in PKU-8: catalytic dehydrogenation ofsec-alcohols withtert-butylhydroperoxide

Catalytic oxidation reaction using green oxidants plays an important role in modern chemical engineering; however, thein situgenerated active species and the related catalytic mechanism need to be understood in depth. For this purpose, Cr-substituted aluminoborate Cr-PKU-8 catalysts were synthesized and applied as recyclable heterogeneous catalysts for the oxidation of aliphatic and aromatic alcohols usingtert-butylhydroperoxide (TBHP). Both high efficiency and selectivity (>99%) were achieved during the dehydrogenation of varioussec-alcohols into acetone in H₂O solvent medium. From the analyses using isotopic tracer, molecular probe and cyclic voltammetry strategies, the chromium ions were observed to undergo a Cr³⁺-Cr²⁺-Cr³⁺redox cycle. DFT calculations suggest thatt-BuOO* is more energetically favourable for hydrogen abstraction fromsec-alcohol thant-BuO*, and probably acts as the key active species. Accordingly, the reaction scheme was proposed to interpret the catalytic process based on the observed results.