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Graphitic carbon nitride (g-C3N4) is a promising photocatalyst for CO2 reduction to alleviate the greenhouse effect. However, the low light absorption, small specific surface area, and rapid charge recombination limit the photocatalytic efficiency of g-C3N4. Herein, we demonstrate a bioinspired nanoarchitecturing strategy to significantly improve the light harvesting and charge separation of the g-C3N4/Au composite, as proven by the remarkable photocatalytic CO2 reduction. Specifically, a biotemplating approach is employed to transfer the sophisticated hierarchical structures and the related light-harvesting functionality of Troides helena butterfly wings to the g-C3N4/Au composite. The resulting g-C3N4/Au composite shows high photocatalytic efficiency under UV–visible excitation with triethanolamine as the sacrificial agent. The yields of CO and CH4 are 331.57 and 39.71 μmol/g/h, respectively, which are ∼36 times and ∼88 times that of pure g-C3N4 under the same conditions. Detailed experiments and the finite-difference time-domain method suggest that the superb photocatalytic activity should be ascribed to the unique periodic hierarchical structure which assists the light absorption and the localized surface plasmon resonance for promoted charge separation in addition to the more effective CO2 diffusion and larger specific surface area. Our work provides a new path for the design and optimization of photocatalysts based on biological structures that are usually unattainable artificially.

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