| Covalent organic framework（COF）is a new kind of organic porous materials,which has structural units such as carbon,hydrogen,oxygen,nitrogen or boron,which are connected by covalent bonds and extend to two or three dimensions.COF has attracted people’s attention for its excellent properties,including high ordered porosity,structural versatility,easy surface modification,excellent thermal and chemical stability.Among them,the more prominent is the COF containing phthalocyanine.Phthalocyanine contains four pyrrole like subunits,which are connected to form a 16 membered ring.Because phthalocyanine has a highly conjugated electronic system,it shows excellent light absorption performance in the visible region,and has excellent thermal and chemical stability.More importantly,the light absorption and redox properties of phthalocyanine can be adjusted by changing the metal center or peripheral substituents.The introduction of phthalocyanine into 2D COF makes theπ-πconjugate system arranged in order,and makes it possible to prepare porous materials such as semiconductors.Zinc 2（3）,9（10）,16（17）,23（24）-tetra-nitrophthalocyanine（Zn Pc-NO2）was synthesized from 4-nitrophthalonitrile and zinc acetate.Reduction of 2（3）,9（10）,16（17）,23（24）-tetranitrophthalocyanine zinc to 2（3）,9（10）,16（17）,23（24）-tetraminophthalocyanine zinc（Zn Pc-NH2）,then Zn Pc-NH2was used to react with p-benzoquinone,1,4-naphthoquinone,and anthracenol,respectively.New covalent organic framework containing phthalocyanine was synthesized:P-Zn Pc COF,N-Zn Pc COF,A-Zn Pc COF.The structure,crystal structure and morphology of P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF were characterized by fourier infrared spectroscopy,nuclear magnetic resonance hydrogen spectrum,N2adsorption-desorption curve and scanning electron microscopy.The results showed that P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF were successfully synthesized.P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF all have large specific surface area and are porous structures with pore size of 2.02 nm,which can store gas.The particle size of P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF is about 100 nm.The properties of P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF were characterized by thermogravimetric,Uv-visible spectrumand cyclic voltammetry.The results show that P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF possess excellent thermal stability.Compared with the precursor Zn Pc-NH2,the Q bands are blue shifted,but red shifted compared with Zn Pc-NO2,and P-Zn Pc COF,N-Zn Pc COF and A-Zn Pc COF have stronger absorbance in the range of300 nm～800 nm.Cyclic voltammetry showed that P-Zn Pc COF,N-Zn Pc COF,A-Zn Pc COF LUMO and HOMO energy levels matched with Ti O2（P25）conduction band,which could be loaded on P25 as photosensitizers.The structure,morphology and properties of the prepared photocatalysts P25/Pt,Zn Pc-NH2/P25/Pt and A-Zn Pc COF/P25/Pt were characterized and analyzed by X-ray diffraction,scanning electron microscope and solid state diffuse reflection ultraviolet spectroscopy.The hydrogen production efficiency of P25/Pt,Zn Pc-NH2/P25/Pt,A-Zn Pc COF/P25/Pt was studied by photolysis of water.The results show that the crystal structure of P25/Pt sensitized by Zn Pc-NH2and A-Zn Pc COF has changed,and the photocatalyst A-Zn Pc COF/P25/Pt sensitized by A-Zn Pc COF has more uniform accumulation,more catalytic active sites and stronger light absorption properties.The hydrogen production efficiency of Zn Pc-NH2/P25/Pt and A-Zn Pc COF/P25/Pt is higher than that of P25/Pt,and the hydrogen production efficiency of A-Zn Pc COF/P25/Pt is the highest,reaching 20.96μmol/h.Dye-sensitized P25 showed stronger photocatalytic performance.Compared with Zn Pc-NH2,A-Zn Pc COF sensitized P25 has stronger photocatalytic performance because the absorbance of A-Zn Pc COF in the range of 300 nm～800 nm basically realizes full absorption.Moreover,A-Zn Pc COF has a porous structure with a large specific surface area,which is easier to load onto P25.It provides an idea for improving the efficiency of hydrogen production from photodissociated water. |
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