Azolate-based metal-organic frameworks and derivatives for electrochemical CO2 reduction reactions: Recent advances and perspectives

The electrocatalytic carbon dioxide reduction reaction (eCO₂RR) is a potential solution to reduce carbon emissions in the future, but there are still challenges in adopting current technology for industrial applications. Therefore, an urgent need is to design and develop active, selective, and stable materials. Among the porous materials, azolate (imidazolate, tetrazolate, triazolate, and pyrazolate) metal-organic frameworks (MOFs) are a subclass of MOFs that have attracted tremendous attention in various applications, specifically eCO₂RR, due to their differentiated key characteristics, i.e., flexible frameworks, abundant active sites, adjustable porosity, high stability, and customized morphology. Despite the salient characteristics and ongoing research, no critical review has been published that covers azolate MOFs for eCO₂RR. This review presents a comprehensive introduction, the conversion mechanism of eCO₂RR, carbon product formation, and strategies for analyzing and identifying products, followed by the chemistry of azolate MOFs, framework design principles, local coordination geometries, synthesis considerations, and the impact of morphology on performance. Subsequently, attention is directed toward surface modification via ligand tailoring, alongside an in-depth examination of structural conductivity, durability, influencing parameters, the role of electrolytes, and the impact of device configuration on performance. Later, recent developments in azolate MOFs and their derivatives and composites are discussed, focusing on the chemical composition and performance of eCO₂RR. Finally, a comprehensive understanding of the most recent advancements, underlying challenges, suggestions, and insights on improving the performance of azolate MOFs for state-of-the-art electrocatalysts has also been presented.