Linker defect engineering for effective reactive site formation in metal-organic framework photocatalysts with a MIL-125(Ti) architecture

Introduction of linker defects in a visible light responsive metal-organic framework (MOF) photocatalyst, MIL-125(Ti)-NH2, has been attempted to improve its reactivity. MIL-125(Ti)-NH2, composed of Ti-oxo cluster and 2-aminoterephthalic acid organic linker, was synthesized by a solvothermal method and then underwent photothermal treatments. XRD measurements and H-1 NMR spectroscopy revealed that linker elimination from the MOF occurred by a simultaneous visible-light irradiation and mild heating at 313 K in water containing electron donor, while keeping its framework structure. The resultant defective MOF effectively promotes visible light-driven H-2 evolution reaction from water containing electron donor without using any cocatalysts, and its activity is comparable to that of Pt cocatalysts-loaded crystalline MIL-125(Ti)-NH2. When pristine MIL-125(Ti)-NH2 without cocatalysts is used in the reaction, the reduction of Ti species in Ti-oxo clusters from Ti4+ to Ti3+ takes place instead of reducing protons to evolve H-2; thereby, linker defect introduction caused by the photothermal treatment was concluded to play a role in creating effective reaction sites for proton reduction on Ti-oxo clusters. (C) 2020 Elsevier Inc. All rights reserved.