Simultaneous benzyl alcohol oxidation and H2 generation over MOF/CdS S-scheme photocatalysts and mechanism study

The conversion from solar energy into storable chemical energy can be achieved through synergistic coupling of photocatalytic H2 production and organic synthesis, during which photogenerated electrons and holes can be simultaneously utilized. Herein, we combined a zirconium-based metal-organic framework, UiO-66-NH2, and CdS nanoparticles (NPs) to form a core-shell structure by a chemical bath method. The step-scheme (S-scheme) heterojunction exhibits both substantially enhanced selective oxidation of benzyl alcohol and efficient H2 generation under light irradiation simultaneously. The electron transfer paths at the S-scheme heterostructure interface were investigated in depth by in situ irradiated X-ray photoelectron spectroscopy. The dynamics of carrier migration at the heterojunction were obtained through femtosecond transient absorption (fs-TA) spectroscopy. Furthermore, the evolution mechanism of benzaldehyde was revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy and electron paramagnetic resonance. This work illustrates the electron transfer mechanism of S-scheme heterojunction by fs-TA spectroscopy and provides new insights into the design of MOF/inorganic composite photocatalysts.