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

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 (k(1 similar to 5)) and activation energies (E-1 similar to 5)) were proposed, and it was indicated that the key to develop this reaction is to reduce cyclopentene oxide hydrolysis activation energy (E-2 and E-4). 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.

Automated summary

The study introduces advanced heterogeneous catalytic materials with multiple acid sites, effective catalytic sites, and directive selectivity for liquid-phase selective oxidation reactions. By investigating the mechanism and key factors, the cooperative catalysis of metal clusters and functional groups in the catalyst are identified as crucial for the excellent performance observed.