Enhanced photocatalytic conversion of greenhouse gas CO2 into solar fuels over g-C3N4 nanotubes with decorated transparent ZIF-8 nanoclusters

The atmospheric concentration of CO2 as the dominant greenhouse gas continues to rise and has become a global environmental issue. Photocatalytic CO2 reduction into solar fuels has been regarded as an ideal solution to reduce CO2 emissions and to use solar energy. Graphitic carbon nitride (g-C3N4) is one of the most promising visible-light-driven photocatalysts for CO2 reduction. Unfortunately, the CO2 reduction performance of g-C3N4 based photocatalyst is normally limited by the inferior charge separation ability and limited CO2 adsorption capacity. In this study, two cooperative strategies, that is, combined host nanostructural design and surface guest grafting, are adopted to overcome the aforementioned drawbacks. Specifically, holey graphitic carbon nitride (g-C3N4) nanotubes were firstly fabricated to modify the light-harvesting ability, the redox potential as well as the charge separation efficiency. And then, the as-prepared tubular g-C3N4 was decorated with suitable amount of transparent zeolitic imidazolate framework-8 (ZIF-8) nanoclusters to further increase CO2 capture capacity without sacrifice of light absorption capacity. Because of the cooperative effects of nanostructural design and surface grafting, the optimized ZIF-8 modified tubular g-C3N4 photocatalysts exhibit a great enhancement in photocatalytic CH3OH production efficiency by more than 3 times, relative to the bulk g-C3N4 (BCN) photocatalyst synthesized by conventional pyrolysis of melamine. This work will enlighten a promising strategy to construct efficient photocatalyst for greenhouse gas CO2 resourcing, by taking advantage of the cooperative effects of semiconductor nanostructures and surface metal-organic framework grafters.