Synchronous Synthesis And Immobilization Of Metal Phthalocyanine On PGMA/SiO₂ And Catalytic Oxidation Performance Of Immobilized Metal Phthalocyanine

Metal phthalocyanine and its derivative, due to its unique macrocyclic conjugated system, not only has good thermal stability and chemical stability, but also has good catalytic activity. It can simulate enzyme catalyst, and catalyze the oxidation of organic compound by oxygen high efficiently under mild conditions. In addition, metal phthalocyanine due to strong absorption in the visible region, in recent years was reported as a photocatalyst for the degradation of organic pollutants in water environment. However, as the catalyst for catalytic reaction, the metal phthalocyanine compound still has some disadvantages, for example, easy aggregation, poor antioxidant capacity, and difficult separation from the reaction system. These defects could be solved by the immobilization of metal phthalocyanine. In this topic, based on poly（methyl methacrylate）（PGMA） and grafted silica（PGMA）, a solid supported metal phthalocyanine was prepared, and its spectral properties and catalytic properties were studied.Firstly,through the ring-opening reaction between the amino groups of tetra amino zinc phthalocyanine（ZnTAPc） and the epoxy groups on the side chains of polyglycidyl methacrylate（PGMA）, the amino zinc phthalocyanine（Zn APc） was bonded onto PGMA, and the ZnAPc modified polymer was gained（denoted as ZnAPc-PGMA）. The chemical structure of ZnAPc-PGMA was characterized by FTIR and 1H-NMR spectra.The effects of the kinds of catalysts and temperature on the bonding process of ZnTAPc on PGMA were investigated by the determination of bonding degree of ZnAPc on PGMA. Their UV-Visible absorption spectra and fluorescence emission spectra were determined, and their photophysical behavior was examined. The experimental results show that ZnAPc-PGMA possess the characteristic electronic absorption and fluorescence emission spectra of zinc phthalocyanine. In addition, they still present some other characters. As ZnTAPc is bonded to PGMA, its aggregability is weakened effectively. And the intensity of the absorption spectra of ZnAPc-PGMA increases with the increasing bound amount of ZnAPc on the side chain of polymer PGMA. However, ZnAPc-PGMA exhibits a polymer effect in its photophysical behavior. As the concentration of ZnAPc units in ZnAPc-PGMA solution is too high, the energy transfer between the adjacent side Zn APc units will be produced, resulting in the slight weakening of the fluorescence emission.The micrometer-sized silica gels were modified chemically by using γ-methacryloxypropyl trimethoxysilane（KH-570） as coupling agent, and double bonds were introduced onto silica gel particles surfaces. Then methyl methacrylate（GMA） was graft-polymerized onto the silica gel particles surfaces using “grafting from” method, and the grafted particles PGMA/SiO₂ were prepared. After that, 4-（4-carboxyl group）-O-benzene phthalonitrile（CPPN）was bonded to the PGMA/SiO₂ through the ring-opening reaction of epoxy bond with carboxyl group, and the CPPN-PGMA/SiO₂ was prepared. The chemical structure of CPPN-PGMA/SiO₂ was characterized by FTIR. The bonding amount of CPPN was determined by the perchloric acid titration. The effects of catalyst, reaction time and reaction temperature on the reaction were explored. The results showed that using triethylamine as catalyst, the bonding reaction was carried at 100℃ for 8 h, then the bonded amount of CPPN in CPPN-PGMA/SiO₂ can be reached up to 0.16 mmol/g.Finally, the metal phthalocyanine was synchronously synthesised and immobilized onto CPPN-PGMA/SiO₂ through the reaction between CPPN-PGMA/SiO₂ and 4-nitro-phthalonitrile and the metal salts（ Co（CH3COO）2·4H2O, Cu（CH3COO）2·H2O,FeCl2·4H2O, Mn（CH3COO）2·4H2O）,and the solid catalyst MNPc-PGMA/SiO₂（M=Co,Fe,Cu,Mn）was prepared. The structure of MNPc-PGMA/SiO₂ was characterized by IR and UV-Vis spectrum. The effects of the dosage of catalyst, reaction time and temperature on the immobilized reaction of metal phthalocyanine were investigated. The results showed that the immobilized reaction was carried out at 140 ℃ for 12 h under the catalyst 1,8-diazabicyclo[5,4,0]undec-7-ene（DBU）, the immobilized amount of cobalt phthalocyanine could reach 16.3 g / 100 g.In order to study the photocatalytic properties of the immobilized metal phthalocyanine catalyst CoNPc-PGMA/SiO₂, the organic dyes methylene blue and rhodamine B were used as target degradation material. The effects of the dosage of CoNPc-PGMA/SiO₂,reaction time and pH on the degradation rate of methylene blue and rhodamine B were investigated mainly. The results showed that under both UV and visible light irradiation, the catalyst CoNPc-PGMA/SiO₂ could catalyze the degradation of both methylene blue and rhodamine B effectively, and the catalytic effect of CoNPc-PGMA/SiO₂ on the degradation of methylene blue was better than that of rhodamine B. The added amount of CoNPc-PGMA/SiO₂, reaction time and pH had a greater impact on the degradation rate of methylene blue and rhodamine B For the degradation reaction of methylene blue, when the amount of Co NPc-PGMA/SiO₂ is 0.09 g（with CoNPc content of 20.35 μmol）, methylene blue can achieve degradation of 80% with 10 minutes of UV irradiation, and 99% of degradation with 30 minutes of UV irradiation; and the degradation of 80% and 99% could still be achieved with 25 minutes and 60 minutes of visible light irradiation seperately. While for the degradation of Rhodamine B, when the amount of CoNPc-PGMA/SiO₂ is 0.09 g（with CoNPc content of 38.44 μmol）, Rhodamine B can achieve degradation of 40% with 40 minutes of UV irradiation, and 55% of degradation with 70 minutes of UV irradiation; and the degradation of 40% and 55% could still be achieved with 80 minutes and 130 minutes of visible light irradiation seperately.MNPc-PGMA/SiO₂（M=Co, Fe, Cu, Mn） was used to catalyze the oxidation of styrene with the molecular oxygen as the oxygen source. By gas chromatography analysis, the main product of the oxidation of styrene was styrene oxide; the effects of various factors on the catalytic performances of MNPc-PGMA/SiO₂ were researched. The results showed that for the oxidation reaction of styrene, the immobilized metal phthalocyanine catalyst MNPc-PGMA/SiO₂ with different center metal showed the different catalytic activity, and CoNPc-PGMA/SiO₂ showed the best catalytic activity. The amount of CoNPc-PGMA/SiO₂ and the reaction temperature had the great influences on the catalytic activity during the oxidation of styrene, and the catalyst existed the best dosage, too much or too little is not conducive to play the catalytic performance of it. When the catalyst is 0.1 g（with CoNPc content of 22.61 μmol）,the reaction, the conversion rate of of styrene reached 99% and the selectivity of styrene oxide was 53% at 100℃ for 6 h. Furthermore, the immobilized catalyst CoNPc-PGMA/SiO₂ had better reusability, the conversion of styrene could still reach 90%, and the selectivity of ethylene oxide could be stabilized at 45% during 5 times of repeated use. All these results indicate that the grafting particles PGMA/SiO₂ can not only protect metal phthalocyanine from aggregation and oxidation, but also promote it to activate O₂.