An anionic MOF as a multifunctional platform for selective adsorption of CO2, separation of organic dyes and ionic conductivity

It is a very effective strategy to capture and separate carbon dioxide by incorporation of alkali cations into MOFs. Presented here is an anionic metal-organic framework (MOF) (Me2NH2)2Co(tpta)center dot 2H2O (1), in which the exchange of alkali ions (Li+ and Na+) took place with H2N(Me)2+ cations. As expected, CO2/N2 selectivity of the framework was improved significantly and reached 61.6 due to the inclusion of Li + using the ideal adsorbed solution theory (IAST) model. The enhancement of its CO2 uptake capability and selectivity has been mainly attributed to the charge-quadrupole interaction. For the CO2/N2 system, it is found that the inclusion of Li+ rather than Na+ favors higher selectivity. Additionally, it successfully separated cationic dye crystal violet (CV+) from anionic dye methyl orange (MO-) by the column-chromatography. Evidently, the enhancement of the electrostatic interaction greatly improves the separation performance of the framework.