From conventional inorganic semiconductors to covalent organic frameworks: advances and opportunities in heterogeneous photocatalytic CO2 reduction

Abstract

Solar-driven photochemical CO₂ reduction over semiconducting materials is a strategic technology towards sustainable development as it represents a source of renewable liquid and gaseous fuels, and simultaneously provides a solution for current environmental problems caused substantially by the accumulation of this greenhouse gas in the atmosphere. However, the unfavorable thermodynamics and the sluggish kinetics of the multi-electron CO₂ reduction reactions pose several challenges in terms of selectivity, conversion efficiencies, and long-term stability. Continuous advances have been made by different research groups on the fundamental understanding of the relationship between the CO₂ conversion efficiency and the physicochemical properties of the photocatalyst. This review aims to present the main findings in this field to a broad audience, starting with the application of conventional inorganic semiconductors as photocatalysts for CO₂ reduction, followed by the introduction of covalent organic frameworks as a new generation of photocatalytic materials. The rational design of organic–inorganic hybrids to enhance the activity and selectivity of the CO₂ reduction is also summarized along with the remaining challenges regarding both fundamental understanding and potential upscaling.