Nitrogen-enriched flexible metal-organic framework for CO 2 adsorption.

A novel MOF named [Zn ₂ (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-1 H -pyrazole-4,1-diyl))tribenzoic acid) and Zn(NO ₃ ) ₂ ·6H ₂ O. This new MOF was characterized by means of different techniques: powder X-ray diffraction, N ₂ 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 CO ₂ at different temperatures was measured and its isosteric enthalpy of adsorption was calculated. The novel MOF shows an uncommon node composed of a Zn ₃ (-COO) ₆ (DMF) ₂ , and the asymmetric unit contains one crystallographically independent linker, one DMF molecule, and two Zn atoms. The [Zn ₂ (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 CO ₂ adsorption capabilities. This material exhibits a low CO ₂ isosteric enthalpy of adsorption ( H _ads ), comparable to previously reported values for similar nitrogenated materials. All the observed CO ₂ adsorption capacities were further supported by DFT calculations.