Temperature Tuned Two Novel 3D Zn(II) Metal Organic Frameworks Exhibiting Luminescence Properties

Two novel porous zinc metal-organic frameworks (MOFs) 1 and 2 based on 1,1′-bis-((3,5-dicarboxybenzyl)-4,4′-bipyridinium) dichloride (H4bdcbpy·2Cl) ligand have been successfully synthesized by solvothermal reactions at different temperatures. Compounds 1 and 2 have the same composition but crystallize in different crystal systems. Compound 1 synthesized at low temperature crystallizes in the monoclinic system, and compound 2 prepared at high temperature crystallizes in the rhombohedral system. The structural differences of two compounds indicate that temperature plays an important role in the formation of the Zn-based MOFs. The Zn2+ ions are bridged by deprotonated formic acid moieties to form a 3D network in both compounds. H4bdcbpy·2Cl provided an acidic environment, which led to the decomposition of DMF into a rare C3H2N22+ cation. Nitrogen adsorption measurement displays that the adsorption capacity of 1 is 711 m2 g–1. The fluorescence spectra of compound 1 shows that there is a strong emission peak at 527 nm.