Effect of pore structures on selective gas sorption behavior of ultramicroporous MOFs

Synthesis, crystal structures and selective gas sorption properties of two new MOFs based on pyrimidyl-5-carboxylate (pmc) are reported. [Co3Cl4(pmc)2(CH3OH)4] (1) possesses pillared layer-type network and narrow one-dimensional channels. In [Fe3(O)(pmc)5.3(O2CH)0.7]·DMF (2), the trinuclear basic carboxylate units form a uninodal 5-connected network with isolated cage-like pores. 1 Shows the selective sorption of hydrogen against nitrogen at 77 K and CO2 against CH4 at 195 K. For 2, a selective sorption is observed only at 77 K, and the sorption is almost indiscriminate at 195 K. This difference is believed to originate from the different pore structures of 1 and 2.

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► We examine selective gas sorptions in two ultramicroporous MOFs.
► Slow diffusion inside narrow one-dimensional channels results in selective sorptions of H2 and CO2.
► MOF with isolated cage-like pores loses selective sorption properties at high temperatures.