A new metal-organic coordination polymer [Zn2(sedc)2(dabco)] (1se; sedc2- = selepophene-2,5-dicarboxylate; dabco = 1,4-diazabicyclo[2.2.2]octane) was synthesized and characterized by single-crystal X-ray diffraction analysis. This MOF is based on {Zn2(OOCR)4N2} paddle wheels and is isoreticular to the family of [Zn2(bdc)2(dabco)] derivatives (1b; bdc2- = 1,4-benzenedicarboxylate) with pcu topology. The gas adsorption measurements revealed that 1se shows a 15% higher CO2 volumetric uptake at 273 K and 28% higher CO2 uptake at 298 K (both at 1 bar) compared to the prototypic framework 1b. Methane and nitrogen adsorption at 273 K was also investigated, and IAST calculations demonstrated a pronounced increase in CO2/CH4 and CO2/N2 selectivity for 1se, compared with 1b. For example, the selectivity factor for the equimolar CO2/CH4 gas mixture at 1 bar = 15.1 for 1se and 11.9 for 1b. The obtained results show a remarkable effect of the presence of selenium atom on the carbon dioxide affinity in the isoreticular metal-organic frameworks with very similar geometry and porosity.
Keywords: X-ray diffraction studies; adsorption measurements; gas adsorption selectivity; porous metal–organic frameworks; selenophene.