Synergistic effects of octahedral TiO2-MIL-101(Cr) with two heterojunctions for enhancing visible-light photocatalytic degradation of liquid tetracycline and gaseous toluene.

The photocatalytic performance of TiO2 is severely restricted by its low photocatalytic activity and high charge-carrier recombination rate. In order to overcome these defects, a novel octahedral TiO2-MIL-101(Cr) (T-MCr) photocatalyst with type-II heterojunction and surface heterojunction is prepared by growth of TiO2 particles on MIL-101(Cr) via optimizing the synthesis conditions. The physicochemical, optical and photoelectrochemical properties of the samples are characterized utilizing several techniques, and its photocatalytic activity for liquid tetracycline and gaseous toluene degradation is evaluated under visible light irradiation. Particularly, the T-MCr-60 shows the outstanding photocatalytic activity. The improved photocatalytic performance of T-MCr-60 is ascribed to strong interfacial contact between (0 0 1) facets, (1 0 1) facets, and MIL-101 and the synergistic effects of two heterojunctions promoting efficient charge transfer. The possible photocatalytic mechanisms involving pollutants degradation pathway and charge transfer mechanisms during the process of pollutants degradation is also discussed.