Computational Study on Metal-Ion-Decorated Prismane Molecules for Selective Adsorption of CO(2) from Flue Gas Mixtures.

Selective adsorption of CO(2) from flue gas is extremely significant because of its increasing concentration in air and its deleterious effect on the environment. In this work, we have explored metal-ion-bound prismane molecules for selective CO(2) adsorption from the flue gas mixture. The Ca(2+)-bound prismane complex exhibits superior CO(2) selectivity and adsorption capacity. The calculated binding energy and molecular electrostatic potential (MESP) analysis showed that the rectangular face of prismane binds strongly with metal ions as compared to its triangular face. The CBS-QB3 and density functional theory-based functional M06-2X/6-311+G(d) calculations show that the prismane molecule can bind to one Li(+), K(+), Mg(2+), and Ca(2+) ion with favorable binding energy. The metal-ion-bound prismane complexes have been examined for their CO(2), N(2), and CH(4) adsorption capacity. Prismane-Ca(2+) can bind with six CO(2) molecules strongly with an average binding energy of -18.1 kcal/mole as compared to six N(2) (-12.6) and five CH(4) (-13.4) gas molecules. The gravimetric density calculated for the CO(2)-adsorbed prismane-Ca(2+) complex has been found to be 69.1 wt %. The discrete hydrocarbon structure for selective separation of CO(2) is rare in the literature and can have potential applications for cost-effective CO(2) capture from the flue gas mixture.