Selective photocatalytic degradation of nitrobenzene facilitated by molecular imprinting with a transition state analog

Photocatalysis with the aid of molecular imprinted photocatalysts provide a highly selective method to remove highly toxic organic pollutants (HTOPs). However, some HTOPs (e.g., nitrobenzene (NB)) cannot be used directly as template due to their low solubility or high toxicity. For removing such HTOPs, the present work designed novel molecularly imprinted polymers (MIP) coated photocatalysts (TSA-MIP-TiO2) by using transition state analog (TSA) as template. For the target pollutant NB, both 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP) were respectively selected as the TSA template to prepare TSA-MIP-TiO2 (2NP-P25 and 4NP-P25). In comparison with neat Degussa P25 TiO2, the obtained TSA-MIP-TiO2 not only increased the photocatalytic degradation of NB, but also inhibited the accumulation of unwanted intermediates. In the presence of bisphenol A (BPA, 225 mu mol L-1) as a non-target pollutant, the photocatalytic degradation rate constants of NB (15 mu mol L-1) over 2NP-P25 and 4NP-P25 were about 4.4 and 3.6 times that over neat P25 TiO2, respectively, whereas the BPA degradation over TSA-MIP-TiO2 was slower than that over neat P25. The much enhanced photocatalytic activity and selectivity can be explained by that TSA-MIP-TiO2 possesses specific molecular recognition to the reaction transition state, which decreases the reaction apparent activation energy. (C) 2013 Elsevier B.V. All rights reserved.