Facile synthesis of M2(m‐dobdc) (M = Fe and Mn) metal‐organic frameworks for remarkable hydrogen storage

Abstract

AbstractMetal‐organic frameworks (MOFs) are emerging as promising candidates for hydrogen storage material because of their porosity and adjustable hydrocarbon structures coordinated with the metal element. Present work explore the synthesis of M2(m‐dobdc) (M = Fe and Mn; m‐dobdc4− = 4,6‐dioxido‐1,3‐benzenedicarboxylate) metal‐organic frameworks via solvothermal method for the purpose of hydrogen storage application. The X‐ray diffraction, transmission electron microscope, scanning electron microscope, energy dispersive X‐ray analysis, and nuclear magnetic resonance spectroscopic studies have been done to ensure the synthesized material is M2(m‐dobdc) (M = Fe and Mn) MOFs. The Brunauer‐Emmett‐Teller (BET) analysis reveals the average pore size of 36.271 nm for Mn2(m‐dobdc) MOF whereas the average pore size for fe2(m‐dobdc) MOF was found to be 2.1992 nm. The as‐prepared MOF samples are in the mesoporous range based on pore size distribution (internal pore diameter greater than 2 nm) with spherical pore geometry. Hydrogen storage studies shows that Fe2(m‐dobdc) has a hydrogen storage capacity of 0.18 wt% at ambient temperature (30°C) under 100 atm H2 pressure, whereas the hydrogen storage capacity for Mn2(m‐dobdc) is 1.38 wt% under identical conditions of temperature and pressure. The hydrogen storage capacity at liquid nitrogen temperature (−196°C) under 100 atm H2 pressure for Fe2(m‐dobdc) and Mn2(m‐dobdc) is 4.31 and 8.21 wt%, respectively.