Photocatalytic oxidation of 4-chlorophenol using thermosensitive zinc phthalocyanine copolymer under visible light irradiation

A novel thermosensitive photocatalyst, P(NIPA-co-ZnMPc), has been prepared using zinc tetra(N-carbonylacrylic)aminophthalocya-nine (ZnMPc) to copolymerize with N-isopropylacrylamide (NIPA). The lower critical solution temperature (LCST) of P(NIPA-co-ZnMPc) measured by differential scanning calorimetry (DSC) was 33.5 degrees C. P(NIPA-co-ZnMPc) effectively catalyzes the oxidation of 4-chlorophenols (4-CP) using oxygen as oxidant under the visible light irradiation, and it has higher photocatalytic activity than ZnMPc under the same condition. The UV-vis spectra of them in aqueous solution indicate that the macromolecular chains in P(NIPA-co-ZnMPc) restrain the aggregation of ZnMPc availably, resulting in the enhanced photocatalytic performance. The results of photocatalytic oxidation at different temperatures show that P(NIPA-co-ZnMPc) presents the highest photocatalytic efficiency around the LCST, suggesting that the macromolecular structure of P(NIPA-co-ZnMPc) can directly influence their photocatalytic activity. The hydrodynamic radius of this copolymer at different temperatures implies the intermolecular hydrophobic aggregation around the LCST, which is advantageous for the enrichment and the photocatalytic oxidation of 4-CP. Due to the high stability of P(NIPA-co-ZnMPc), it can be cyclically used in homogeneous photocatalytic oxidation and heterogeneous separation.