Intrinsic metal organic frameworks as electro-catalysts for water splitting

Abstract

The joint of metal organic frameworks (MOF) as exceptional electro-catalysts brings a new era for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Various types of MOF-analogues, MOF-composites, and MOF-derivatives are extensively investigated for accelerating the reaction kinetics and thereby improving the faradic efficiency. In this review article, we give a short review of the intrinsic MOFs reporting in the recent four years (2021–2024), especially for those synthesized by the thermal-treatments lower than 200 °C to maintain their intrinsic crystal structures. In order to deliver a comprehensive correlation between the intrinsic MOF architecture and the electrochemical contribution toward water splitting, possible structural collapse of MOFs, additives, binders, mixtures, and composites are excluded. Then several types of intrinsic MOFs are categorized by the molecular structures of ligands into three groups: (1) homocyclic ligands; (2) heterocyclic ligands; (3) mixed ligands. Homocyclic ligands include (i) benzene-1,4-dicarboxylic acid (BDC), (ii) functionalized BDC, (iii) macrocyclic BDC, and (iv) benzene-1,3,5-tricarboxylic acid (BTC). Heterocyclic ligands include (i) imidazole-based and (ii) triazole-based analogues. Mixed ligands include different combinations between homocyclic and heterocyclic ligands. Among these intrinsic MOFs, synergistic effects and future perspectives raised by applying macrocyclic MOFs, mixed-metal MOFs, and heterogeneous MOF-on-MOF assembly are highlighted.