Design of Fe-MOF-bpdc deposited with cobalt oxide (CoOx) nanoparticles for enhanced visible-light-promoted water oxidation reaction

This work spotlights the facile method to deposit cobalt oxide (CoO x ) 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 O 2 . Due to the soft conditions needed for the process developed, the framework structure of Fe-MOF-bpdc was maintained even after the deposition of CoO x . The optimized CoO x @Fe-MOF-bpdc composite showed enhanced activity towards visible-light-driven WOR as compared to pristine Fe-MOF-bpdc, the amount of evolved O 2 being increased by about 2 times at the maximum with CoO x loading of 2 wt% as Co metal. Investigations on the wavelength dependence of visible-light-driven WOR on CoO x @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 CoO x deposition, suggesting that CoO x acts as a unique hole trapping site and more preferentially catalyse the four-electron oxidation reactions like WOR than the two-electron oxidation reaction.