TiO 2 @NH 2 -MIL-125(Ti) composite derived from a partial-etching strategy with enhanced carriers’ transfer for the rapid photocatalytic Cr(VI) reduction

Metal-organic frameworks (MOFs)-based composites have been widely applied as photocatalysts because of their synergistic effect between the two individual component. Herein, TiO 2 @NH 2 -MIL-125(Ti) nanocomposites which possess unsaturated titanium—oxo clusters, mesoporous structure, and intimate interface were successfully constructed via an in-situ distilled water-etched route. The X-ray photoelectron spectroscopy (XPS) measurements indicated strong electronic interaction between TiO 2 and NH 2 -MIL-125(Ti), confirming the formation of TiO 2 @NH 2 -MIL-125(Ti) nanocomposite. Photoelectrochemical and thermodynamics measurements showed that TiO 2 @NH 2 -MIL-125(Ti) nanocomposites have improved charge separation efficient and decreased transfer resistance of the carriers within the heterojunction interfaces, which facilitates the photoexcited electrons transfer and reduction of the Cr(VI) species. Therefore, the optimal TiO 2 @NH 2 -MIL-125(Ti) nanocomposite demonstrated superior performance compared to NH 2 -MIL-125(Ti) and NH 2 -MIL-125(Ti) derived TiO 2 . Based on the free radical trapping experiment and electron paramagnetic resonance (EPR) measurements, a possible type-II scheme was proposed for the enhanced photocatalytic activity over the TiO 2 @NH 2 -MIL-125(Ti) nanocomposite.