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• A photothermal treatment for MIL-125(Ti)–NH 2 achieved creation of linker defects in its framework. • 18.4% of linkers could be eliminated while maintaining the framework structure. • The defective MIL-125(Ti)–NH 2 effectively promoted visible light-driven H 2 evolution reaction. • The reactivity of the defective MOF was comparable to that of Pt-loaded MIL-125(Ti)–NH 2. • Defect sites on Ti-oxo clusters behaved as effective reaction sites for proton reduction. Introduction of linker defects in a visible light responsive metal–organic framework (MOF) photocatalyst, MIL-125(Ti)–NH 2 , has been attempted to improve its reactivity. MIL-125(Ti)–NH 2 , 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 1H 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)–NH 2. When pristine MIL-125(Ti)–NH 2 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. [ABSTRACT FROM AUTHOR]

This work spotlights the facile method to deposit cobalt oxide (CoOx) nanoparticles as a cocatalyst on Fe-MOF-bpdc to enhance its photocatalytic activity for water oxidation reaction (WOR) under visible light irradiation to evolve gaseous O2. Due to the soft conditions needed for the process developed, the framework structure of Fe-MOF-bpdc was maintained even after the deposition of CoOx. The optimized CoOx@Fe-MOF-bpdc composite showed enhanced activity towards visible-light-driven WOR as compared to pristine Fe-MOF-bpdc, the amount of evolved O2 being increased by about 2 times at the maximum with CoOx loading of 2 wt% as Co metal. Investigations on the wavelength dependence of visible-light-driven WOR on CoOx@Fe-MOF-bpdc revealed that the direct photo-excitation of Fe-oxo clusters within Fe-MOF-bpdc plays an important role to initiate the reaction. Furthermore, it was found that the rate of 2-propanol oxidation reaction, which is a typical two-electron oxidation reaction, was hardly affected by CoOx deposition, suggesting that CoOx acts as a unique hole trapping site and more preferentially catalyse the four-electron oxidation reactions like WOR than the two-electron oxidation reaction. [ABSTRACT FROM AUTHOR]