The Synthesis, Characterization And Applications Of Organic-inorganic Hybrid Zirconium Phosphonates Based On Azobenzene Which Contain Hydroxyl, Carboxyl, Sulfonic Acid Groups

Azobenzene compounds have photoisomerization properties. They go through reversible trans(?)is isomerization upon irradiatio at a specific wavelength, which cause significant change in molecular structure and dipole moment, resulting in changes in their physical and chemical properties. In recent years, azobenzene compounds have attracted focus research attention in materials science due to their widespread potential application in information storage, optical switches, photochromic, and so on. When azobenzene moiety is grafted to organic-inorganic hybrid materials by copolymerization, the obtained hybrid materials also possess reversible trans(?)cis isomerization upon irradiatio at a specific wavelength, this provides a theoretical basis for this paper. In this paper, three azobenzene monomers were prepared, and three kinds of azobenzene organic-inorganic hybrid zirconium phosphonates were subsequently prepared by copolymerization. The chemical structure, morphology, and properties of the azobenzene monomers and the hybrid materials were characterized. The effect of skeleton of the hybrid materials on the photoisomerization rate was investigated. The detailed research contents were described as follows:1. Preparation, characterization and application of organic-inorganic hybridazobenzene zirconium phosphates.Two functional azobenzene monomers,4-(6-phosphate) hexyloxy-4’-hydroxy azobenzene (PAC6AZOOH) and 4,4’-bis (6-phosphate) hexyloxy azobenzene (DiPAC6AZO), were prepared via esterification, substitution, and hydrolyzation reactions using 4,4’-dihydroxyazobenzene as the starting material. Four azobenzene zirconium phosphonates, mono-substituted 4-hydroxy-azobenzene organic zirconium phosphonate (ZrOPC6AZOOH), mono-substituted organic-inorganic hybrid 4-hydroxy-azobenzene zirconium phosphonate (ZrOPPC6AZOOH), di-substituted azobenzene organic zirconium phosphonate (ZrOPC6AZO) and di-substituted organic-inorganic hybrid azobenzene zirconium phosphonate (ZrOPPC6AZO), were subsequently synthesized by reacting of PAC6AZOOH and DiPAC6AZO with eight hydrated zirconium oxychloride (ZrOCl2·8H2O). The azobenzene monomers were characterized by 1H NMR and 13C NMR, and the hybrid materials were characterized by SEM, FT-IR, XRD, TG, SEM, and N2 adsorption desorption analysis. By combination of photoirradiation induced isomerization and N2 adsorption desorption analysis, we found for the first time that photoirradiation induced reversible trans (?)cis isomerization of azobenzene chromophore could change the specific surface area of the material, and this process is reversible. These materials as gas adsorbent were investigated. Among nitrogen, hydrogen, methane, and carbon dioxideand, these materials showed better property toward nitrogen.2. Preparation and characterization of organic-inorganic hybrid 4-carboxyazobenzene zirconium phosphateAn azobenzene functional monomer 4-(6-phosphate)hexyloxy-4’-carboxyazobenzene (PAC6AZOCOOH) was synthesized using 4-hydroxy-4’-carboxyazobenzene as the starting material. Two azobenzene zirconium phosphonates,4-carboxyazobenzene zirconium phosphonate (ZrOPC6AZOCOOH) and organic-inorganic hybrid 4-carboxy azobenzene zirconium phosphonate (ZrOPPC6AZOCOOH), were prepared by reacting of PAC6AZOCOOH with ZrOCl2·8H:0 via esterification, substitution, and hydrolyzation reactions. The azobenzene monomer was characterized by 1H NMR and 13C NMR, and the hybrid materials were characterized by SEM, FT-IR, XRD, TG, SEM, and N2 adsorption desorption analysis.3. Preparation, characterization, and application of organic-inorganic hybrid 4-sulfonicazobenzene zirconium phosphatesThe azobenzene-based functional monomer 4-(6-phosphate)hexyloxy-4’-sulfonicazobenzene (PAC6AZOSO3H) was synthesized by esterification, substitution, and hydrolyzation reaction with 4-hydroxy-4’-sulfonicazobenzene. Two azobenzene zirconium phosphonates, organic 4-sulfonicazobenzene zirconium phosphonate (ZrOPC6AZOSO3H) and organic-inorganic hybrid 4-sulfonicazobenzene zirconium phosphonate (ZrOPPC6AZOSO3H), were prepared by reacting of PAC6AZOSO3H with eight hydrated zirconium oxychloride (ZrOCl2·8H2O). The monomer was characterized by 1H NMR,13C NMR, and the zirconium phosphonate materials were characterized by SEM, FT-IR, XRD, TG, SEM and N2-adsorption desorption analysis. The ZrOPPC6AZOSO3H was used as catalysts for the Mannich reaction in water using benzaldehyde, aniline, and cyclohexane as the reactants with excellent yield. The catalyst can be used multiple times and no significant decrease in efficiency.