Research On The Assembly Of Metal-organic Triangles And Its Photocatalytic Hydrogen Production

Hydrogen acquires a high combustion calorific value and only produces water during combustion,so it is considered as an alternative,sustainable and clean energy.Artificial photosynthetic hydrogen production is regarded as an effective way to convert and utilize solar energy.Building an efficient,low-cost,nontoxic and chemically stable photocatalytic system is a goal that scientists have always pursued.The current research mainly focuses on the three aspects of photocatalytic hydrogen production semi-reaction,visible light-driven hydrogen decomposition and hydrogen production coupled with visible light catalysis organic conversion.At present,scientists have developed artificial photocatalytic systems for the generation of hydrogen from water based on molecular photosensitizers and semiconductor light-capturing materials.The efficiency and stability of photocatalytic hydrogen production have been continuously improved.The metal organic supramolecular complexes with nanoscopic shape and size and welldefined hydrophobic cavities are regarded as mimics of natural photocatalytic system by catching organic dyes in their pockets.Compared to other relevant systems,these supramolecular architectures are superior in light-driven hydrogen production by enhancing the proximity between the organic dye or photosensitizer and the catalytic center and by increasing the effective local concentration of the substrates within the container.Therefore,the main work of this paper includes the following two parts:First,we designed and synthesized one double-armed Schiff-base ligand DPQ,and constructed [3+3] metal-organic macrocycle structure Co-DPQ by coordinating with transition metal Co(?).Through ESI-MS,electrochemical and fluorescence quenching titration experiments,it has been confirmed that there is a host-guest interaction between the metal threemembered ring Co-DPQ and the guest fluorescein molecule,and a 1: 1 host-guest inclusion complex is formed.A three-component photolysis hydrogen production system with catalyst Co-DPQ,photosensitizer fluorescein and electron sacrificial agent triethylamine was constructed.Under the best hydrogen release conditions,Co-DPQ shows better hydrogen production efficiency and stability of photolysis water as a photocatalyst,and the TON value of hydrogen production can reach 1580.Second,a cobalt based metal-organic [3+3] self-assembly macrocycle was constructed by tridentate Schiff-base ligand with N,O and P atoms.The functionalized metal-organic triangle with amino groups was connected to photoactive fluorescein isothiocyanate(FITC)via postassembly modification strategy,which was used as photocatalyst for hydrogen evolution from water splitting.It's a two-component system for hydrogen production without extra photosensitizer.Besides,compared with the three-component system,the post-modified synthetic metal complex catalyst Co-DPQ-FITC exhibited higher photocatalytic activity at the same metal catalyst and photosensitizer concentration with a turnover number(TON)of 80 mol hydrogen per mole catalyst,which was approximately 30 times the photocatalytic efficiency of Co-DPQ.