Hierarchical Co3O4/ triple-shelled carbon nitride ( Co3O4/TSCN) composite nanocapsules were designed via a multi-step procedure in a controlled manner as a solar-light-driven photocatalyst based Z-scheme system for selective aerobic photooxidation of alcohols (primary and secondary aliphatic and benzylic) to corresponding aldehydes/ or ketones in green media. The structure of the as-prepared photocatalyst was characterized by a series of measurement techniques including FT-IR, XRD, BET, TEM, FE-SEM, EDX, EDX-mapping, TGA, UV–vis DRS, and ICP-OES. The hierarchical Co3O4/ TSCN composite nanocapsules demonstrated superior photocatalytic activity in selective aerobic oxidation of alcohols under solar light irradiation in comparison to pure TSCN and Co3O4 NPs. The shell number of the composite nanocapsules and the formation of the hierarchical Co3O4/ TSCN Z-scheme photocatalyst can significantly affect the photocatalytic activity. The results indicate the efficient electron transfer, relatively high specific surface area, high donor density, and low band gap as well as the coexistence of micro-, meso- and macropores and also nano-sized crystalline structure (from 1.2 to 95 nm) in heterojunction composite. This novel photocatalytic system kept relatively high catalytic activity after five recycle runs under the same reaction conditions.

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