Nitrogen-enriched flexible metal–organic framework for CO2 adsorption

Abstract

A novel MOF named [Zn₂(L)(DMF)] was synthesized using solvothermal methods from the reaction of the new linker (4,4′,4′′-(4,4′,4′′-(benzene-1,3,5-triyltris(methylene))tris(3,5-dimethyl-1H-pyrazole-4,1-diyl))tribenzoic acid) and Zn(NO₃)₂·6H₂O. This new MOF was characterized by means of different techniques: powder X-ray diffraction, N₂ adsorption and desorption isotherms, thermogravimetric analysis, and scanning electron microscopy. Furthermore, suitable crystals were obtained, which allowed us to perform the X-Ray structure determination of this MOF. The capability of these new MOF to adsorb CO₂ at different temperatures was measured and its isosteric enthalpy of adsorption was calculated. The novel MOF shows an uncommon node composed of a Zn₃(–COO)₆(DMF)₂, and the asymmetric unit contains one crystallographically independent linker, one DMF molecule, and two Zn atoms. The [Zn₂(L)(DMF)] MOF is a microporous material with high crystallinity and stability up to 250 °C. The multiple nitrogenated pyrazole linkers in its framework enhance its CO₂ adsorption capabilities. This material exhibits a low CO₂ isosteric enthalpy of adsorption (H_ads), comparable to previously reported values for similar nitrogenated materials. All the observed CO₂ adsorption capacities were further supported by DFT calculations.