A cobalt-based MOF with the synergistic effect of size sieving and multi-functional sites for selective gas adsorption

An ultramicropore MOF , {[Co 6 (5-MIA) 5 (tmbpy)(μ 3 -OH) 2 (ethanol) 2 ]∙(ethanol) 2 } n ( 2 ) (5-H 2 MIA= 5- methoxyl-isophthalic acid; tmbpy ​= ​3,3′-dimethyl-4,4′-bipyridine), was rationally designed and constructed. The gas sorption behavior of 2 for C 2 H 2 , CO 2 , CH 4 , CO, and N 2 was investigate by experiments. The C 2 H 2 and CO 2 uptakes of the activated sample ( 2a ) were up to 64.87 ​cm 3  ​g −1 and 63.97 ​cm 3  ​g −1 at 273 ​K (100 ​kPa), respectively. Specifically, 2a possesses 3.5 ​Å of aperture and multi-functional sites (open Co 2+ sites and methoxy groups), resulting in the synergistic effect of size sieving and host-guest interactions for selective adsorption of carbon dioxide (or acetylene). The IAST selectivities of C 2 H 2 /CH 4 (1:1) and CO 2 /CH 4 (1:1) on 2a were 26.6 and 12.3 ​at ambient temperature and 100 ​kPa, respectively. The easy regeneration, outstanding humid/thermal stability, and good reusability, make it a promising candidate for industrial application of the separation of C 2 H 2 /CH 4 , CO 2 /CH 4 , CO 2 /N 2 and CO 2 /CO.