Synthesis and characterization of zinc-organic frameworks with 1,4-benzenedicarboxylic acid and azobenzene-4,4'-dicarboxylic acid
Van Hung Nguyen, Ngoc Phuong Thuy Nguyen, Thi Tuyet Nhung Nguyen, Thi Thanh Thuy Le, Van Nghiem Le, Quoc Chinh Nguyen, That Quang Ton, Thai Hoang Nguyen and Thi Phuong Thoa Nguyen
Abstract
The solvothermal reactions of 1,4-bezenedicarboxylic acid (H2BDC) or azobenzene-4,4'-dicarboxylic acid (H2ABD) 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 H2BDC:Zn mole ratio of 1:1 and H2BDC concentration of 0.1 M. At more dilute H2BDCconcentration of 0.01 M and H2BDC:Zn mole ratio of 1 : 4, the reaction product was cubic crystals (BZ2) with a size of 250 μm. In the H2ABD system, flat-plate-like crystals (AZ1) were obtained at H2ABD:Zn mole ratio of 1 : 1 and H2ABD concentration of 0.01 M. Meanwhile, thick-block-like crystals (AZ2) were formed at the same H2ABD:Zn mole ratio but at 0.004 M H2ABD. The Langmuir surface area (SLang) of the materials was remarkable, enhanced by diluting the reaction solution. For the compounds synthesized in N,N'-dimethylformamide (DMF), SLang increased from 304.6 m2 g−1for BZ1 to 2631 m2 g−1 for BZ2 and from 475.8 m2 g−1 for AZ1 to 3428 m2 g−1 for AZ2. Meanwhile, BZ2 synthesized in N,N'-diethylformamide (BZ2/DEF) got the highest SLang of 4330 m2 g−1. Both AZ2 and BZ2 materials were stable up to 400 °C
