Synthesis and characterization of zinc-organic frameworks with 1,4-benzenedicarboxylic acid and azobenzene-4,4′-dicarboxylic acid

Abstract

Abstract The solvothermal reactions of 1,4-bezenedicarboxylic acid ( H 2 BDC ) or azobenzene-4,4′-dicarboxylic acid ( H 2 ABD ) with zinc ions/clusters lead to the formation of four crystalline materials. All of these compounds were characterized by x-ray diffraction, optical microscopy, thermo-gravimetric analysis and nitrogen adsorption. Block-shaped crystals (BZ1) with various shapes and sizes were obtained at H 2 BDC:Zn mole ratio of 1:1 and H 2 BDC concentration of 0.1 M. At more dilute H 2 BDC concentration of 0.01 M and H 2 BDC:Zn mole ratio of 1 : 4, the reaction product was cubic crystals (BZ2) with a size of 250 μ m . In the H 2 ABD system, flat-plate-like crystals (AZ1) were obtained at H 2 ABD:Zn mole ratio of 1 : 1 and H 2 ABD concentration of 0.01 M. Meanwhile, thick-block-like crystals (AZ2) were formed at the same H 2 ABD:Zn mole ratio but at 0.004 M H 2 ABD . The Langmuir surface area ( S Lang ) of the materials was remarkable, enhanced by diluting the reaction solution. For the compounds synthesized in N , N ′-dimethylformamide (DMF), S Lang increased from 304.6 m 2 g −1 for BZ1 to 2631 m 2 g −1 for BZ2 and from 475.8 m 2 g −1 for AZ1 to 3428 m 2 g −1 for AZ2. Meanwhile, BZ2 synthesized in N , N ′-diethylformamide (BZ2/DEF) got the highest S Lang of 4330 m 2 g −1 . Both AZ2 and BZ2 materials were stable up to 400 ° C .