Immobilization of tungsten chelate complexes on functionalized mesoporous silica SBA-15 as heterogeneous catalysts for oxidation of cyclopentene

An efficient hybrid mesoporous heterogeneous catalyst system was synthesized via covalently grafting tungsten chelate complex W-N,N (N,N = (3-triethoxysilylpropyl) [3-(2-pyridyl)-1-pyrazolyl] acetamide, N,N-chelating ligand) in organic moieties (diphenyldichlorosilane, DPHS)-functionalized mesoporous silica SBA-15 or pure SBA-15. Characterization of synthesized materials via N2 sorption, XRD, TEM, UV–Vis DRS, 29Si MAS NMR, element analysis, and FT-IR indicated that W-N,N was successfully anchored and highly dispersed in the mesochannels of SBA-15 and the mesostructure of SBA-15 was maintained during the grafting course. The synthesized hybrid catalysts were highly active and authentically heterogeneous in triphasic oxidation reaction of cyclopentene (CPE) with H2O2. W,N-N immobilized on functionalized SBA-15 with DPHS moieties (W-N,N-DPHS-SBA-15) showed better catalytic properties (activity and stability) than its unmodified counterpart W-N,N-SBA-15 catalyst. Besides, possible catalytic reaction route for CPE oxidation with H2O2 over W-N,N-DPHS-SBA-15 catalyst was proposed. The amphiphilic mesochannels of W-N,N-DPHS-SBA-15 provided suitable accommodation for both hydrophilic H2O2 and hydrophobic CPE molecules and acted as nanoreactors for CPE/H2O2/solid triphase reaction.