In or on, a study of the influence of the binding site for TiO and MIL-101(Cr).

In this work, TiO was formed in the internal pores and on the surface of MIL-101(Cr). Density functional theory (DFT) calculations demonstrate that the difference in the binding sites of TiO can be attributed to the different solvents used. The two composites were used to photodegrade methyl orange (MO), and the photocatalytic efficiency of TiO-in-MIL-101(Cr) (90.1% in 120 min) was much stronger than that of TiO-on-MIL-101(Cr) (14% in 120 min). This is the first work to study the influence of the binding site of TiO and MIL-101(Cr). The results show that MIL-101(Cr) modification with TiO can promote electron-hole separation, and TiO-in-MIL-101(Cr) has better performance. Interestingly, the two prepared composites have distinct electron transfer processes. For TiO-on-MIL-101(Cr), radical trapping and electron paramagnetic resonance (EPR) studies show that O˙ is the main reactive oxygen species. Based on its band structure, it can be concluded that the electron transfer process of TiO-on-MIL-101(Cr) conforms to that of a type II heterojunction. However, for TiO-in-MIL-101(Cr), the EPR and DFT results show that O is the active substance that is formed from O through energy transfer. Therefore, the influence of binding sites should be considered for the improvement of MOF materials.