Intelligent light-responsive and ionic polymer functionalized polyacrylonitrile as an environmental benign catalyst for selective oxidation of benzyl alcohols

Herein, spiropyran (SPA) and 1-vinyl-3-ethylimidazole were firstly grafted as conjugated polymer onto the Polyacrylonitrile fiber (PANF) by reversible addition fragmentation chain transfer (RAFT), and then their imidazole cation were used as exchanger to prepare an intelligent photo-responsive catalyst loaded with intact Keggin hydrogen phosphotungstate (HxPW12O40 (3-x) -), which were fully characterized by FT-IR, XPS, SEM, TGA and ICP. The obtained catalysts could efficiently promote the aqueous oxidation of benzyl alcohol in presence of H2O2. The reversible light-responsive property of SPA on fiber renders its hydrophobic microenvironment which is propitious to adsorb organic starting substrates in the reaction process, while the increasing hydrophilicity, derived from the ring opening of SPA by ultraviolet light, can desorb the product completely from the fiber. The whole catalytic process, including reaction stage and work-up stage, does not need any volatile organic solvent and the catalysts could be recycled for 10 times without any significantly loss of activity. Finally, the fiber could be further twinned on the impeller of mechanical stirrer, demonstrating the readily scale-up production potential.