Self-directed Assembly Of The Functionalized Porphyrin Assemblies And Their Photocatalytic Performance For Hydrogen Production

Metalloporphyrins, with highly conjugated planar structures and chromophore, are a kind of important organic macrocyclic ligands, and show excellent photosensitivity. They have drawn many researchers'attentions for their widely used in various fields, such as optoelectronic devices, catalysis, and molecular recognition. For the modified structure, metalloporphyrin can be used as ideal candidates for constructing porphyrin-based assemblies with higher thermal stability and chemical stability, more excellent physical and chemical properties than metalloporphyrin monomers. The purpose in this thesis is to synthesize a new type of porphyrin monomers with special structure and reaction activity, and to fabricate a series of metalloporphyrin assemblies with excellent performance by self-directed assembly of the monomers. The porphyrin monomers with substituents located at axial and peripheral directions were vital to fabricate functionalized porphyrin-based assemblies with high photoelectric activity and stability. Furthermore, photocatalytic activity for hydrogen production from water reduction was investigated, and effects of various kinds of metal ions on hydrogen production over the metalloporphyrin assemblies were also explored. The main contents are listed as the followed:A series of tetra (4-hydroxyphenyl) metalloporphyrins were synthesized with tetra (4-hydroxyphenyl) porphyrins and various metal salts as the main reactants. Products were characterized by UV-Vis, FT-IR, MS and 1H NMR.Five kinds of silanized metalloporphyrins monomers (SMPM) were prepared by using 5,10,15,20-tetra(4-hydroxyphenyl) metalloporphyrin (MTHPP) and y-isocyanatopropyltriethoxysilane (ICPTES) as the reactants. Due to the axial coordination between y-isocyanatopropyltriethoxysilane and metalloporphyrin, and horizontal reaction between hydroxyl groups and ICPTES, SMPM were achieved. Products were characterized by UV-Vis, FT-IR, MS and 1H NMR.A novel silanized metalloporphyrin cobalt monomer (SMPCM) was prepared by using 5,10,15,20-tetra(4-hydroxyphenyl)porphyrin cobalt (CoTHPP) and ICPTES as the reactants. Followed by the hydrolysis-polymerization of the organosilanes in the axial direction and peripheries of the SMPCM, the ordered porphyrin thin films with uniform morphology were facilely prepared on various substrates by the self-directed assembly of the SMPCM. The thin films formed were characterized by UV-vis spectra, electron microscopies, X-ray diffraction spectra, Fourier transform infrared spectra, fluorescence spectra and X-ray photoelectron spectra. The results demonstrated that the axial assembly between the Co3+ ion in the center of porphyrin macrocycle and ICPTES can prevent porphyrin lamellar from curling in horizontal direction, and then enhance the order and stability of the films. Especially, the thin films possessed high, sensitive and stable photoelectronic response.New type of metalloporphyrin-based assemblies were fabricated by the self-directed assembly of the SMPM precursors. Catalytic performance of metalloporphyrin-based assemblies was investigated. Furthermore, the influence of metal ions in the center of metalloporphyrins on the photocatalytic performance was explored.Method used in the preparation of porphyrin assemblies in this thesis was simple, mild and novel. Moreover, the target products showed high photoelectric activity and photocatalytic activity for hydrogen production from water reduction. It paved a new, way for fabricating other porphyrin-based assemblies with excellent performance.