Adsorption Induced In‐situ Construction of TiO2 Hollow Sphere/UiO‐66‐NH2 Heterostructures with Boosted Photocatalytic Activity toward Cr(VI) Reduction

Water contamination caused by highly toxic Cr(VI) should be resolved imminently with more efficient photocatalytic approach. The interaction between photocatalyst heterostructure is critical for charge separation which largely affect photocatalytic efficiency. Herein, TiO2 hollow sphere/UiO-66-NH2 (TiO2/UiO-66-NH2) heterostructures were successfully synthesized by an adsorption induced in-situ solvothermal growth strategy. The UiO-66-NH2 particles were well dispersed on TiO2 hollow spheres by solvothermal treatment of Zr4+ adsorbed TiO2 hollow spheres with NH2-BDC ligand. The photocatalytic activities of TiO2/UiO-66-NH2 heterostructures were investigated by reduction of Cr(VI) with visible light irradiation. With the introduction of UiO-66-NH2, the reduction efficiency toward Cr(VI) by TiO2/UiO-66-NH2 heterostructures reached 89% after 180 min of irradiation, which is much higher than those of TiO2 hollow spheres (10%) and UiO-66-NH2 crystals (29%). Moreover, the TiO2/UiO-66-NH2 heterostructures display good regeneration ability and can still maintain 70% of Cr(VI) removal ability after four cycles. The integration of TiO2 and UiO-66-NH2 could construct a type-II heterojunction to broaden the absorption range of light and suppress the recombination of photoproduced electrons and holes. As a result, such unique composite structure significantly enhance the photocatalytic performance towards Cr(VI) reduction. This work not only inspires a new approach for in-situ solvothermal synthesis of semiconductor@MOFs composites, but provides a novel photocatalyst for highly efficient removal of Cr(VI) from wastewater.