Inorganic molecular imprinted titanium dioxide photocatalyst: synthesis, characterization and its application for efficient and selective degradation of phthalate esters

An inorganic molecular imprinted polymer (IMIP) coated photocatalyst for photodegradation of diethyl phthalate (DEP) was synthesized by coating a layer of molecular imprinted silica/alumina on the surface of TiO2 nanoparticles with DEP as the template. The characterization with HR-TEM, XRD, FT-IR and UV-visible spectroscopic analysis indicated that the new catalyst was a composite of the TiO2 particle core and a shell layer of Al3+-doped silica with thickness of about 5 nm. The Al-27 MAS NMR measurements revealed that the IMIP layer consisted of framework tetrahedrally coordinated aluminium and non-framework octa-coordinated aluminium species, both of which function as the hot spots for the adsorption of target molecules on the catalyst during photocatalysis. It was found that the IMIP layer provided the photocatalyst with molecular recognition ability, leading to selective adsorption and rapid mineralization of the target pollutant from its low level solution (2 mg L-1) in the presence of other high level non-target pollutants, such as phenol (50 mg L-1). Unlike the neat TiO2 photocatalyst (Degussa P25), the use of the IMIP-coated TiO2 photocatalyst almost eliminated the generation of toxic aromatic byproducts. Moreover, the new photocatalyst was totally constructed by inorganic compounds, being resistant to photochemical attack and showing favorable lifetime during the photocatalysis.