Improving the Separation of CO/N Using Impregnation of a Deep Eutectic Solvent on a Porous MOF.

As the partial pressure of CO in flue gas is 0.1-0.2 bar, CO capture at a low pressure needs more attention. Under low pressure conditions, the functional metal-organic framework (MOF) is powerful for CO capture. One of the effective methods to increase the absorption capacity of the MOF is impregnation with deep eutectic solvents. In this research, NH-MIL101(Cr) is impregnated with a deep eutectic solvent of choline chloride:urea (DES ChCl:urea) to enhance the adsorption capacity. The CO and N adsorption capacity of NH-MIL101(Cr) and DES/NH-MIL101(Cr) was investigated at temperatures of 288.15-303.15 K and pressures up to 1 bar. The obtained results indicate that the adsorption capacity of the MOF increases by 1.7 and 3 times with the impregnated DES for CO and N, respectively. Nevertheless, the pore volume of the MOF decreased after impregnation, but the adsorption capacity of the MOF increased due to the interaction of the adsorbate with the confined DES in pores. The contribution of the impregnated DES to adsorption capacity is explained according to Henry's law. Also, high heats of adsorption are attributed to the strong interaction between modified NH-MIL101(Cr) and CO. Also, the sample was refined at 298 K and vacuum and was reused without considerable reduction of the CO capture capacity after 6 times. Moreover, the impregnation of ChCl:urea into NH-MIL101(Cr) nanostructures was studied using density functional theory-based approaches.