An iron-based metal–organic framework for selective CO2 adsorption and as an efficient anode material for lithium-ion batteries

Abstract

Given the versatility of electronic properties induced by the synergic effect of metal-oxo clusters and multifunctional organic ligands, metal–organic frameworks (MOFs) have emerged as prospective materials for energy-related applications such as gas storage/separation and electrochemical storage. In this study, an iron-based MOF, namely, Fe-CPB (CPB = 1,2,3,4,5,6-hexakis(4-carboxyphenyl)benzene) was successfully synthesized via a solvothermal reaction and fully characterized. Taking advantage of the permanent porosity, the layered structure with high π-conjugation derived from a hexaphenylbenzene core, and polar carboxylate and acetate groups connected by infinite iron-oxo chains, Fe-CPB has been examined for its selective CO₂ adsorption properties and electrochemical performance when applied as an anode material for lithium-ion batteries. As a proof-of-concept, Fe-CPB showed a moderate low-pressure CO₂ uptake (40 cm³ g⁻¹ at 273 K), high isosteric heat of CO₂ adsorption (33 kJ mol⁻¹), and good CO₂ selectivity over N₂ and CH₄. As an anode material for rechargeable lithium-ion batteries, Fe-CPB exhibited a high reversible capacity of 634 mA h g⁻¹ with 99% capacity retention after 100 cycles (at a current density of 100 mA g⁻¹). Interestingly, Fe-CPB showed a high rate capability with a discharge capacity of 416 mA h g⁻¹ (at a current density of 2000 mA g⁻¹) and 673 mA h g⁻¹ when the current density was returned to 100 mA g⁻¹. Our result envisaged the potential of developing MOFs for energy applications including CO₂ separation and electrodes of rechargeable batteries.