Room temperature synthesis of an Fe(ii)-based porous MOF with multiple open metal sites for high gas adsorption properties

Abstract

An iron(II)-based porous metal-organic framework, [NH₄][Fe₂(OH)(BTtC)(BPz)_0.5(H₂O)(DMF)]·DMF·3H₂O, has been constructed using 1,2,4,5-benzenetetracarboxylic acid (H₄BTtC) and bispyrazole (BPz) as ligands. Single crystals were obtained using the solvent diffusion technique at room temperature. It contains hydroxo bridged dinuclear Fe(II) centers and features water and DMF coordinated to Fe(II) centers representing the open metal sites. The framework is anionic in nature and contains rectangular open channels with 43% void volume and a 4,10-connected binodal net. Gas adsorption properties showed that it can adsorb up to 60 cc g⁻¹ and 27 cc g⁻¹ of CO₂ gas at 273 and 298 K respectively, while 54 cc g⁻¹ of H₂ gas at 77 K. Argon adsorption studies showed that the BET surface area is 458 m² g⁻¹.