Preparation and characterization of novel cyclohexene-to-adipic acid catalyst with ionic liquid phosphotungstate immobilized on MIL-101 nanocages based on Cr-N coordination

In this study, a series of MIL-101-X catalysts were prepared by confining acidic ionic liquid phosphotungstate in MIL-101 nanocages using the organic electron-rich N-heterocyclic compound as a chemical bridge and the aforementioned catalysts were used for the oxidation of cyclohexene to adipic acid. During the aforementioned process of post-synthetic modification, a Bronsted acidic ionic liquid phosphotungstate ([C 3 SO 3 Hnhm] 3 PW 12 O 40 ) was synthesized in the nanocage of MIL-101. The research results reveal that the yield of adipic acid for the cyclohexene oxidation catalyzed by the constructed MIL-101-X catalyst was up to 78.16% in solvent-free condition. And its catalytic activity is not significantly reduced after six cycles. The novel catalyst synthesized in this paper combines the common advantages of ionic liquid phosphotungstate and MIL-101 nanocage microenvironment to facilitate the diffusion of reactants and their interaction with the catalytic activity center. This research will provide a new idea to solve the problem in terms of the shortage of efficient catalysts in the field of catalytic oxidation of cyclohexene to adipic acid.