Three novel MOFs constructed from 1,3,5-tris(1-imidazolyl)benzene and dicarboxylate ligands with selective adsorption for C 2 H 2 /C 2 H 4 and C 2 H 6 /CH 4 .

The urothermal reactions of Co(II)/Zn(II) salts with the diverse carboxylic acid and 1,3,5,-tris(1-imidazolyl)benzene(tib) ligands afforded three novel MOFs, namely, [Co 3 (tib) 2 (abdc) 2 (ox)] 2 ·6H 2 O (1), [Co 3 O(tib)(abdc) 2 (DMI)]·2DMI·2H 2 O (2) and [Zn 3 I 2 (tib) 2 (napdc) 2 ]·2DMI·2H 2 O (3), (H 2 abdc = 5-amino-1,3-benzenedicarboxylate, H 2 napdc = 1,4-naphthalene dicarboxylic acid and DMI = 1,3-dimethyl-2-imidazolidinone). In compounds 1 and 2, the Co(II) atoms are connected by polycarboxylate ligands to form two-dimensional (2D) layers that are pillared by tib ligands leading to the formation of 3D porous frameworks. In compound 3, the Zn(II) atoms are linked by tib ligands to form one-dimensional ribbon-like chains which are further connected by polycarboxylate ligands, making a 3D framework possible. Compound 1 can selectively adsorb unsaturated hydrocarbon molecules (C 2 H 2 and C 2 H 4 ) and saturated hydrocarbon molecules (C 2 H 6 and CH 4 ). Specifically, compound 1 has high IAST selectivity for acetylene and methane (0.50 : 0.50, v/v) at 273 K and 1 bar. DFT calculations reveal that the π-conjugated hexagonal carbon ring may be the primary adsorption site because there are π-π interactions between the unsaturated hydrocarbon molecules (C 2 H 2 and C 2 H 4 ) and the π-conjugated hexagonal carbon ring in the framework of compound 1.