Selective CO 2 uptake and inverse CO 2/C 2H 2 selectivity in a dynamic bifunctional metal-organic framework

Abstract

The unique bifunctional porous metal-organic framework, [Co(HL dc)]·1.5MeOH·dioxane, incorporates both free-standing carboxyl and pyridyl groups within its pores. Gas adsorption measurements on the desolvated framework reveal unusual selective CO 2 adsorption over C 2H 2 and CH 4 linked to a framework phase change from a narrow pore (np) to a large pore (lp) form, mediated by CO 2 uptake at 195 K. This phase transition has been monitored by in situ powder X-ray diffraction and IR spectroscopy, and modelled by Grand Canonical Monte Carlo simulations revealing that the reversible np to lp transition is linked to the rotation of pyridyl rings acting as flexible "pore gates". © 2012 The Royal Society of Chemistry.