Construction of Highly Porous Pillared Metal-Organic Frameworks: Rational Synthesis, Structure, and Gas Sorption Properties.

Different from the conventional method to construct pillared-layer metal-organic frameworks (MOFs) by using mixed bipyridyl and dicarboxylate ligands, herein, we present a new approach to build pillared-layer frameworks based on the pyridyldicarboxylate ligands which were predesigned with a certain shape. As exemplified, the ligands of 3-(2',5'-dicarboxyphenyl)benzoic acid (Hdbba) and 3-(2',5'-dicarboxylphenyl)pyridine acid (Hdcpy) were selected and employed to construct three pillared-layer MOFs, [Zn(dbba)(bipy)(DMF)]·3DMF·4HO (1) (bipy = 4,4'-bipyridine), and a pair of crystal polymorphs of [Zn(dcpy)]·1.5DMF·1.5HO (2 and 3), under solvothermal reactions, respectively. In the structures of 1-3, the [Zn(COO)] clusters are bridged by the terephthalate units of dbba/dcpy to form 2D layers; these layers are further pillared by bipy and the benzoate units of dbba or the pyridine units of dcpy to furnish the 3D frameworks. All of them possess high porosity characterized by N adsorption and exhibit high selective adsorption of CH and CO over CH.