Review and prospects of microporous zeolite catalysts for CO2 photoreduction

Abstract

Light-driven CO2 conversion into valuable chemicals is the most promising pathway for minimizing the greenhouse effect and producing alternative energies. A wide variety of photocatalyst, cocatalyst, and Z-scheme component compositions for CO2 photoreduction (CO2PR) have been extensively studied. However, research focusing on microporous zeolite-based photocatalysts for CO2PR is scarce, compared to that of semiconductor-based photocatalysts. This review article is a comprehensive guide of the most recent developments and future prospects of microporous zeolite-based photocatalysts with respect to CO2PR. Apart from photoreduction, this article also briefly discusses studies on thermal reduction for the comprehensive understanding of CO2 reduction over zeolites, with the aim of introducing new ideas for future zeolite-based photocatalyst designs. Herein, we briefly review the fundamentals of CO2PR mechanisms and zeolite crystallography. We then discuss the seven major configurations of zeolite-based photocatalysts applied to CO2PR, namely (i) single heterocation species on and (ii) single heteroatom substitutions in the zeolite framework, (iii) metal and (iv) metal oxide clusters embedded in zeolite caves, dispersion of (v) metal and (vi) metal oxide nanoparticles on the zeolite surface, and (vii) integration with polymeric semiconductors. Most of these materials are naturally photocatalytically active, owing to the unavoidable presence of trace amounts of heteroatoms in zeolites. Reported strategies that further improve their photocatalytic performance for CO2 conversion are also discussed in this article. The introduction of some specific configurations on microporous zeolite-based photocatalysts results in a synergistic effect on CO2PR. Zeolite nanosheets improve the reactant/product mass transfer in CO2PR, while zeolite-based Z-scheme photocatalysts enhance visible light absorption, charge transfer, and separation. Throughout the article, we offer a rich description of these techniques by providing mechanistic insights, application areas, and possible potentials for the development of innovative zeolite-based photocatalysts.