Photocatalytic removal of pentachlorophenol by means of an enzyme-like molecular imprinted photocatalyst and inhibition of the generation of highly toxic intermediates

Pentachlorophenol (PCP) is a typical highly-toxic pollutant, and its direct photolysis and conventional photocatalysis may produce more toxic by-products such as dibenzodioxins. It is urgently needed to develop a photocatalytic process able to remove PCP without the generation of highly toxic by-products. To achieve this, enzyme-like molecular-imprinted photocatalysts were prepared by using structural analogues of PCP as pseudo templates. It was found that 2,4-dinitrophenol (DNP) was the best template among the tested analogues. The molecular imprinted polymer (MIP) coated P25 TiO2 photocatalyst DNP-P25 prepared with DNP as the template greatly accelerated the photocatalytic degradation of PCP and depressed the generation of toxic intermediates. It was confirmed that the amino groups at the footprint cavities provided a well-defined micro reaction environment, which made the benzene ring of the adsorbed PCP be better exposed to photo-generated reactive OH radicals, leading to easier cleavage of the benzene ring. Both the intermediate analysis and toxicity evaluation confirmed that the MIP-coated TiO2 can make the photocatalytic degradation a safe and green approach of removing PCP.