A heterostructured ZnAl-LDH@ZIF-8 hybrid as a bifunctional photocatalyst/adsorbent for CO2 reduction under visible light irradiation

A heterostructured ZnAl-LDH@ZIF-8 hybrid largely enhances its photocatalytic CO2 reduction ability. [Display omitted] •A novel photocatalyst/adsorbent hybrid of ZnAl-LDH@ZIF-8 was prepared.•The hybrid showed a high visible-light-response activity and high selectivity for CO2 reduction.•The mechanism on photocatalysis and adsorption of ZnAl-LDH@ZIF-8 hybrid was revealed.•The structure–activity relationship of ZnAl-LDH@ZIF-8 hybrid was studied in detail.•The photocatalytic performance of ZnAl-LDH@ZIF-8 hybrid was 7.0 times higher than ZnAl-LDH. Artificial photocatalytic technology is widely used to reduce atmospheric CO2 and convert it into a series of available carbon containing fuels. Among a series of photocatalysts, LDH (layered double hydroxides) and ZIF (zeolitic imidazolate framework) materials have attracted interest of many researchers because of their special physical and chemical properties. In this work, we center on the technical problems of LDH and ZIF in photocatalytic CO2 reduction process, we combined the respective advantages of LDH and ZIF materials to design a new heterostructured ZnAl-LDH@ZIF-8 hybrid photocatalyst/adsorbent, which had a wide range of visible light response, high activity and high selectivity. Through a series of structural characterizations, the results revealed that ZnAl-LDH as a catalyst was excited and produced photoelectric charge under the excitation of sunlight. Meanwhile, the CO2 adsorbed on the catalyst surface was reduced to CO by photogenerated electrons which were migrated from ZnAl-LDH to ZIF-8 surface. The ZnAl-LDH@ZIF-8 hybrid showed a remarkable photocatalytic CO2 conversion of 9.03 μmol·g−1·h−1 and a high selectivity of 97.77%. In addition, the effect on the excitation transfer of photoelectric charge and photocatalytic CO production of interaction between ZnAl-LDH and ZIF-8 were studied, and the relationships among catalyst compositions, surface structures, photoelectric properties, and catalytic performances were clarified. This research supplies a significant method for the construction and development of new type photocatalyst/adsorbent heterostructure, and provides new viewpoints and technical support for in-depth understanding of photocatalytic CO2 reduction.