Photo-thermal Catalytic CO Methanation by RuO@MIL-101(Cr) with 9.2% Apparent Quantum Yield under Visible Light Irradiation.

Solar-assisted gaseous CO hydrogenation to CH is a potential strategy for favoring the transition to net zero emissions. Here, we report the development of a series of efficient metal-organic frameworks with MIL-101(Cr or Fe) topology decorated with RuO nanoparticles (ca. 0.2-2 wt %) as heterogeneous photocatalysts for the selective methanation of CO by H under simulated sunlight irradiation. The activity of RuO(1 wt %)@MIL-101(Cr) is between 3 and 50 times higher than related MOF-based photocatalysts under similar reaction conditions. Among the different photocatalysts, the optimized RuO(2 wt %)@MIL-101(Cr) photocatalyst showed 98.1% CO conversion with 98.8% CH selectivity reaching a production rate of 7.85 mmol g h with 720 mW cm at 200 °C. Further, this photocatalyst exhibited a record apparent quantum yield of 9.2% at 600 nm and 200 °C after subtracting thermal activity contribution compared to any previous MOF- or other heterogeneous-based photocatalyst reported so far. The photocatalyst retained its activity and integrity upon reuse for about 110 h. Transient photocurrent, electrochemical impedance, photoluminescence, and laser flash photolysis spectroscopies together with additional photocatalytic experiments suggest the occurrance of dual photochemical and photothermal reaction pathways. The photocatalytic CO methanation reaction mechanism was further investigated using Fourier transform infrared spectroscopy.