Covalent immobilization of TiO2 within macroporous polymer monolith as a facilely recyclable photocatalyst for water decontamination
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This study focused on the covalent immobilization of TiO2 on the surface of a porous polymer monolith by a two-step method. Firstly, porous polymeric monolith with trimethoxysilane anchor groups was fabricated by w/o emulsion templated copolymerization of vinyl acetate (VAc) and methacryloxypropyl-trimethoxysilane (MPS). Then, anatase TiO2 were covalently immobilized within the voids of poly(VAc-MPS) monolith via an acid-catalyzed co-condensation of the trimethoxysilane group with a TiO2 sol precursor at low temperate. Scanning electron microscopy images demonstrated that both poly(VAc-MPS) and Ti-P(VAc-MPS) possess dense honeycomb-like macroporous structures. The chemical structure analysis by Fourier transform infrared spectroscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy revealed that (i) acid-catalyzed sol-gel method in this case could fully convert the amorphous TiO2 sol to anatase TiO2 even at low temperature (70°); (ii) TiO2 particles were covalently immobilized within the voids of the polymer monolith via Si–O–Ti linkage; (iii) acid-catalyzed hydrolysis of the trimethoxysilane groups and VAc led to significant increase in the hydrophilicity of the obtained hybrid porous monolith, Ti-P(VAc-MPS), with a water contact angle of 19.6°. Exemplified by the photo-degradation of methyl orange (MO) in aqueous solution, Ti-P(VAc-MPs) exhibited good photocatalytic activity and excellent recyclability for water decontamination. The as-prepared Ti-P(VAc-MPS) monolith could be efficiently regenerated for cyclic runs without further energy-consuming separation process such as centrifugation and filtration. The present approach opens a green way for obtaining other porous inorganic-organic photocatalyst for water contaminant removal.
KeywordsTiO2 Photocatalysis polyHIPE Porous Ti–O–Si linkage Separation-free
The authors are grateful to the National Natural Science Foundation of China (Grant nos. 51403140 and 51573109) and the State Key Lab of Polymer Material Engineering Foundation (No. sklpme 2015-2-01 and 2016-3-02) for supporting this research.
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Conflict of interest
The authors declare that they have no conflict of interests.
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