Synthesis Of Supramolecular And Polymeric Photoactive Centers Of Fe-Hydrogenase And Their Photocatalytic Properties

Hydrogenase in nature can efficiently catalyze proton reduction to produce hydrogen,each hydrogenase active center can produce 6000-9000 hydrogen molecules per second.Researchers have done a lot of work in the field of simulating natural iron hydrogenase,but the artificial hydrogenase has the disadvantages of poor stability and low activity.Metal-organic frame materials have the characteristics of large specific surface area,excellent thermal stability,easy to adjust pore size and functional modification,which can not only be directly used to support substrate molecules,but also can be used to support substrate molecules through the exchange of ligands on the skeleton and substrate molecules.The[Fe-Fe]-hydrogenase structural unit was self-assembled with metal ions to form a stable metal-organic framework,and the[Fe₂S₂]active center was fixed in the tunnel of the metal-organic framework to improve its stability and photocatalytic activity.In this paper,we designed and synthesized organic ligands of iron hydrogenase with terminal cyanogen as ligands,self-assembled them with metal ions,obtained several coordination polymers,and studied their photocatalytic hydrogen production activities.1.Designed and synthesized two organic ligands of iron hydrogenase with cyano-containing ligands as ligands and self-assembled with silver salts to obtain three coordination polymers.For the first time,three coordination polymers containing active sites of[Fe₂S₂-Ag_x]-hydrogenase were synthesized.Notably,Ag-S bonding between the Ag center of the[Fe₂S₂]cluster and the S atom resulted in a new[Fe₂S₂-Ag_x]（x=1 or 2）catalytic site in all three polymers.The results of photochemical hydrogen production experiments showed that compared with ligands L1,L2 and1 containing[Fe₂S₂-Ag₁],the catalytic performance of 2 and 3 containing[Fe₂S₂-Ag₂]was significantly improved.2.According to the literature,organic photosensitive ligands containing benzothiazoles were synthesized,and a coordination polymer was obtained by self-assembly with silver salt.A series of organic ligands containing oxadiazole rings were designed and synthesized on the basis of terminal cyanogen.During the synthesis process,the organic ligand of one-arm iron hydrogenase containing oxadiazole ring at one end and ethyl at the other end was accidentally obtained,and several polymers were obtained by self-assembly with silver salt.Organic ligands or coordination polymers containing nitrogen heterocyclic iron hydrogenase were used as photocatalysts,ruthenium photosensitizers and iridium photosensitizers were used respectively,and the optimal photocatalytic hydrogen production conditions of iron-containing hydrogenase ligands and coordination polymers were explored by changing the types of proton sacrifice agents,such as triethylamine,triethanolamine,ascorbic acid,and changing the PH value of solvents.In summary,by changing the temperature and solvent conditions,we realized for the first time the direct coordination between the organic ligand of[Fe-Fe]-Hydrogenase and metal salt to obtain the coordination polymer.The photolysis water test showed that the hydrogen production performance of the coordination polymer was better than that of the ligand.It is expected to improve the hydrogen production efficiency of iron hydrogenase by changing the conditions and try to obtain high-dimensional coordination polymers by introducing heterocyclic rings.