Catalytic efficiency and kinetic analysis of manganese Polyoxometalate Heterogenized in MIL-100-Fe for selective Olefin oxidation using H2O2

Abstract

In our previous study, we introduced a heterogeneous catalyst, denoted as H5[PMo11MnO39(H2O)]0.30@ [Fe3O(OH)(H2O)2[C6H3(CO2)3]2·8H2O (C1), through the encapsulation of a homogeneous polyoxometalate, H5[PMo11Mn(H2O)O39] (MnP), within a metal–organic framework [Fe3O(OH)(H2O)2[C6H3(CO2)3]2·14H2O (MIL-100-Fe). In the present study, we utilized the same catalyst for the oxidation of cyclohexene (CyH), cis-cyclooctene (CyO), styrene (Sty), and geraniol (Ger) in acetonitrile, employing H2O2 as a green oxidant. Kinetic studies were carried out to investigate the influence of substrate, H2O2, catalyst concentration, reaction time, temperature, and total H2O2 decompositions on oxidation and selectivity. C1 exhibited significantly higher efficiency in catalyzing the allylic oxidation of all substrates compared to individual components MnP and MIL-100-Fe, in terms of conversion percentage, rate constants, turnover numbers (TONs), H2O2 efficiencies, and product selectivity. Under optimized conditions, C1 achieved overall conversions of 85 %, 96 %, 98 %, and 100 % for CyH, CyO, Sty, and Ger, respectively. The harmonious catalytic function of polyoxometalates (POM) and metal-organic frameworks (MOF) in C1 also reduced the auto-decomposition of H₂O₂ which resulted into higher H2O2 efficiencies. Notably, the catalyst exhibited complete recoverability and reusability without any structural changes or loss of activity.