A microporous metal-organic framework with unusual 2D → 3D polycatenation for selective sorption of CO2 over CH4 at room temperature

Abstract

By appealing to the pillared-layer strategy, a new Zn(II)-based microporous polycatenated metal-organic framework {[Zn2(bpydb)2(EtOH)(4-bpdb)](DMF)4(EtOH)2}n (1, bpydb = 4,4′-(4,4′-bipyridine-2,6-diyl)dibenzoate, 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene, DMF = N,N-dimethylformamide) with Lewis basic sites on the pore surface has been designed and generated by the solvothermal reaction of mixed ligands (bpydbH2 and 4-bpdb) and Zn(NO3)2 · 6H2O. The structure of 1 displays a 3D pillared-bilayer network generated from polycatenation of the 2D bilayers with an accessible solvent void of 43%. Its porosity has been verified by the N2 sorption at 77 K, which reveals a BET surface of 545 m2/g and pore volume of 0.324 cm3/g. Moreover, compound 1 shows excellent adsorption selectivity for CO2 over CH4 around room temperature, which has been correlated to the specific interaction of CO2 with functional azine groups that decorated the pore channels.