Metal-organic frameworks and their derivatives as bifunctional electrocatalysts

The mass distribution of clean and renewable technologies, such as fuel cells, metal-air batteries and hydrogen production, heavily relies on the efficiencies of underlying electrocatalytic reactions, namely, oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Tremendous efforts have already been invested in the syntheses and applications of metal-organic framework-based (MOF) electrocatalysts, due to their fascinating functionalities and diversities. Recent advances demonstrate keen interests and ambitions to achieve bifunctional catalytic activity in MOF-based catalysts, particularly targeting specific energy conversion applications, namely, ORR/OER for metal-air batteries, HER/OER for electrocatalytic water splitting. The unique characteristics of MOFs make it possible to design and grant MOF-based catalysts excellent bifunctional catalytic performance by means of incorporating bimetallic components, associating with non-metallic elements, hosting and exposing bifunctional active sites/species. Herein, this review aims to summarize recent explosive number of researches on MOF-based bifunctional catalysts with particular attention to the origin of bifunctionalities and the fundamental principles in designing bifunctional MOF-based catalysts. Current challenges and future prospects for bifunctional MOF-based catalysts are proposed before the conclusion of this review as well.