In this study, a series of novel BiNbO 4 and BiNbO 4 /reduced graphene oxide (BiNbO 4 /r-GO) visible-light photocatalysts were prepared. Pure BiNbO 4 was prepared by simple co-precipitation; on the other hand, BiNbO 4 /r-GO composites were prepared by simple mechanical mixing, followed by hydrothermal treatment. The effect of r-GO on the structural, surface morphological, and optical properties of the prepared photocatalysts was investigated using ultraviolet−visible (UV−vis) diffuse reflectance spectroscopy (UV−vis DRS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and Brunauer−Emmett−Teller (BET) for the determination of the specific surface area and porosity and energy-dispersive X-ray spectroscopy (EDX) for determining the elemental composition. A red shift in optical band gap measurements was observed with the increasing r-GO mass percentage in the prepared BiNbO 4 /r-GO composites. Photocatalytic activities of pure BiNbO 4 and the composites were evaluated using the photocatalytic cycloaddition of carbon dioxide to propylene oxide as a model reaction. All the prepared photocatalysts produced cyclic propylene carbonate selectively with no polymeric material observed. The highest photocatalytic efficiency was achieved using BiNbO 4 /5% r-GO composite photocatalyst, where the mass percentage of r-GO was 5%.

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We report the fabrication of a novel metal−organic framework (MOF)−polymer mixed-matrix flexible membrane for the detection of hydrogen sulfide (H 2 S) gas at room temperature. This high-performance gas sensor is based on MOF-5 microparticles embedded on a conductivity-controlled chitosan (CS) organic membrane. The conductivity of the organic membrane is controlled by blending it with a glycerol ionic liquid (IL) at different concentrations. The sensor showed a remarkable detection sensitivity for H 2 S gas at a concentrations level as low as 1 ppm at room temperature. The MOF-5/CS/IL gas sensor demonstrates a highly desirable detection selectivity, fast response time (<8 s), recovery time of less than 30 s, and outstanding sensing stability averaging at 97% detection with 50 ppm of H 2 S gas. This composite having high sensitivity, low-power consumption, and flexibility holds great promise for addressing current challenges pertinent to environmental sustainability.

Chemistry and applications of metal–organic frameworks (MOFs) based on s-block metal ions have been comprehensively reviewed. This work underlines the importance of diversifying the structures of s-block MOFs for various applications.