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A highly efficient, non-toxic, metal-free, low-cost, acid–base bifunctional sulfonated graphitic carbon nitride (S-g-C3N4) nanosheets for Knoevenagel condensation and multicomponent tandem reactions under environmentally benign conditions.

The development of efficient photocatalysts for utilization of solar energy for water splitting coupled with oxidation of biomass-derivatives is of utmost importance for the simultaneous production of clean fuel (H2) and value-added chemicals. Consequently, herein we report the development of the Z-scheme photocatalytic system, Zn0.5Cd0.5S/xMnO2, which has the optimum band structure suitable for efficient visible-light-assisted photocatalytic H2 generation integrated with selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to a more value-added product, 2,5-diformylfuran (DFF). The electron microscopy analyses of the samples revealed the presence of Zn0.5Cd0.5S microspheres composed of smaller nanocrystals with the surface covered by the MnO2 nanostructure and the intimate contact between Zn0.5Cd0.5S and MnO2. Photocatalytic investigations revealed the highest activity for Zn0.5Cd0.5S/1%MnO2, affording a DFF yield of 46% and a simultaneous H2 generation rate of 1322 μmol g–1 in 24 h, which are, respectively, 9 and 4 times higher than those of parent sample, Zn0.5Cd0.5S. Further, the best heterostructure exhibits good catalytic activity even under natural sunlight irradiation, affording DFF with a 14% yield and H2 generation rate of 152.6 μmol g–1 in 6 h. The high catalytic activity of the heterostructure over the parent materials has been attributed to efficient separation of photogenerated charge-carriers with the aid of the Z-scheme mechanism and the synergistic catalysis between Zn0.5Cd0.5S and MnO2. Overall, this work represents a unique demonstration of noble metal-free selective oxidation of HMF to DFF integrated with H2 production under mild reaction conditions.

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Photocatalytic production of clean fuel hydrogen (H2) from water using semiconductor nanomaterials as photocatalysts aided by natural sunlight represents a promising means to fulfill the growing energy demand and for mitigating increasing concentration of atmospheric CO2 due to the burning of fossil fuels. Among the widely studied semiconductor nanomaterials, the CdxZn1−xS ternary system has gained significant interest due to its tunable band edge, optical and electronic properties by merely varying the Cd2+/Zn2+ content. Consequently, CdxZn1−xS‐based nanostructures have been extensively studied as promising visible‐light‐active photocatalysts for H2 production from water and other photocatalytic transformations. Herein, a comprehensive account of the research progress in the development of CdxZn1−xS‐based photocatalysts for the production of solar fuel, H2 from water is provided. Further, various strategies used in enhancing the photocatalytic activity of CdxZn1−xS photocatalysts, like control of the morphology (0D, 1D, 2D, and 3D), bandgap engineering, and fabrication of various heterostructures have been discussed in detail. Furthermore, opportunities and future perspectives of CdxZn1−xS‐based photocatalysts for practical applications have also been discussed. Overall, the importance of CdxZn1−xS‐based photocatalysts is showcased for efficient visible‐light‐driven hydrogen production and can be beneficial for the design of sustainable photocatalytic systems.