Mono-substituted polyoxometalate clusters@Zr-MOFs: Reactivity, kinetics, and catalysis for cycloolefins-H2O2 biphase reactions

Abstract

Abstract Advanced heterogeneous catalytic materials, mono-substituted polyoxometalate clusters@Zr-MOFs (i.e., M-POM@Zr-MOFs, M= Co or Cu), with multi-acid sites, effective catalytic sites, stable active sites, and directive selectivity are reported and applied in liquid (cycloolefin)-liquid (H2O2) biphase selective oxidation system. One of the M-POM@Zr-MOFs crystals, Co-POM@UiO-bpy, when acted as the catalyst for cyclopentene selective oxidation, displayed excellent catalytic ability (76.3 % cyclopentene conversion and 95.0 % glutaric aicd selectivity) and superior cycling stability. Further investigation uncovered that this excellent catalytic performance could be assigned to the cooperative catalysis of metal clusters (i.e., Zr-OH(OH2)) in Zr-MOFs host framework, the gust Co-POM molecules, and the functional groups (viz., bipyridines). Moreover, for the first time, a set of mechanism steps for cyclopentene oxidation with detailed kinetic parameters (i.e., reaction rate constants (k1∼5) and activation energies (E1∼5)) were proposed, and it was indicated that the key to develop this reaction is to reduce cyclopentene oxide hydrolysis activation energy (E2 and E4). This work provides a new option for the development of POM@MOFs catalysts and supplies a new perspective for cycloolefins selective oxidation to dicarboxylic acids.