Efficient and Reusable Polymer Supported Copper(II) and Vanadium(IV) Complexes of 4-(Furan-2-ylmethyleneamino)benzoic Acid as Catalysts for the Oxidation of Phenol

This study reports the synthesis, characterization and catalytic evaluation of polymer supported Cu(II) and V(IV) complexes for the oxidation of phenol. The heterogeneous catalysts were prepared by covalently immobilizing 4-(furan-2-ylmethyleneamino)benzoic acid onto chloromethylated polystyrene followed by coordination with the respective metal ions. Elemental analysis, spectroscopic characterization and ligand-to-metal stoichiometry confirmed successful complex formation, with metal loadings of 1.40-1.41 mmol g–1. The vanadium complex exhibited square-pyramidal geometry with a V=O bond, while the copper complex having a square-planar geometry. The catalytic activity was evaluated using H2O2 and tert.-butyl hydroperoxide (TBHP) as oxidants under varying reaction conditions. The Cu(II) catalyst with TBHP achieved a maximum phenol conversion of 94.9% and catechol selectivity of 76.3% under optimized conditions. X-ray diffraction, BET analysis, and thermogravimetric analysis revealed a predominantly amorphous, mesoporous structure with a specific surface area of 54.05 m2 g–1 and thermal stability up to approximately 335 ºC. Spectroscopic analysis confirmed structural stability after repeated catalytic use, while atomic absorption spectroscopy revealed negligible metal leaching over five cycles. These results establish the potential of polymer-supported Cu(II) and V(IV) complexes as reusable heterogeneous catalysts for phenol oxidation.