In Situ Construction of MIL-100@NiMn-LDH Hierarchical Architectures for Highly Selective Photoreduction of CO2 to CH4

Layered double hydroxides (LDHs) are considered a promising catalyst for photocatalytic CO2 reduction due to their broad photoresponse, facile channels for electron transfer, and the presence of abundant defects. Herein, we reported for the first time the fabrication of a novel photocatalyst MIL-100@NiMn-LDH with a hierarchical architecture by selecting MIL-100 (Mn) as a template to provide Mn3+ for the in situ growth of ultrathin NiMn-LDH nanosheets. Moreover, the in situ growth strategy exhibited excellent universality toward constructing MIL-100@LDH hierarchical architectures. When applied in the photocatalytic CO2 reduction reaction, the as-prepared MIL100@NiMn-LDH exhibited excellent CH4 selectivity of 88.8% (2.84 mu mol h(-1)), while the selectivity of H-2 was reduced to 1.8% under visible light irradiation (lambda > 500 nm). Such excellent catalytic performance can be attributed to the fact that (a) the MIL-100@NiMn-LDH hierarchical architectures with exposed catalytic active sites helped to enhance the CO2 adsorption and activation and (b) the presence of rich oxygen vacancies and coordinately unsaturated metal sites in MIL-100@NiMn-LDH that optimized the band gap and accelerated the separation/transport of photoinduced charges.

Automated summary

In this study, a novel photocatalyst MIL-100@NiMn-LDH with a hierarchical architecture was successfully fabricated. It showed excellent selectivity in the CO2 reduction reaction, with CH4 selectivity reaching 88.8%. The superior catalytic performance can be attributed to the exposed catalytic active sites and the presence of abundant oxygen vacancies and coordinately unsaturated metal sites.