The Synthesis,structures,properties And Applications Of Inorganic–organic Hybrid Polymers Based On Pyridine Ligands

Pyridine ligands have large conjugated delocalized?bonds,which can construct inorganic-organic hybrid polymers(IOHPs)with excellent stability and diverse properties through coordination bonds,hydrogen bonds,and?-?stacking among aromatic rings.IOHPs materials have good development prospects in the fields of photocatalysis,photoelectrocatalysis,gas sorption,and light sensing.In this paper,2organic bipyridine ligands,4,4,-bis(4-pyridyl)biphenyl and 6-bis(4-pyridyl)naphthalene with bigger delocalized electon systems,and SCN^-and halide ions were used as auxiliary ligands were used to react with inorganic metal ions in suitable reaction conditions,resulted in obtaining 7 target IOHPs through controlling various reaction conditions.The paper systematically explored the crystal structures,luminescence performance,thermal stability,photocatalytic performance,photoelectrochemical performance,and structure-activity relationship of the target IOHPs.The main results are addressed as follows.1.Using 4,4'-bis(4-pyridyl)biphenyl(Bpbp)as the main ligand and halogen ions as the auxiliary ligands to react with inorganic metal ions,5 target IOHPs([Pb(Bpbp)X₂]_n(X=Cl 1,Br 2,I 3),[Hg(Bpbp)X₂]_n(X=Br 4,I 5))were obtained.X-ray single crystal diffractions show that IOHP 1,2,and 3 display two-dimensional layered structures,while IOHPs 4 and 5 display one-dimensional zigzag chain structures.The solid-state UV diffuse reflections show that the band gaps of IOHP 1,2 and 3 decrease in order.The solid-state fluorescence tests data also show that the luminescence mechanism of IOHP 1,IOHP 2 and IOHP 3 are the similar,and the luminescence of the three IOHPs all originate from ligand-to-ligand charge transition.The performance tests of IOHPs 1,2 and 3 as photocatalysts shows that the hydrogen production performance of IOHPS 1and 2 are not good,while the hydrogen production performance and stability of IOHP 3is relatively good.The hydrogen production of IOHP 3 for 3 consecutive 3 hours hydrogen production performances are 4.87,3.6 and 3.7?mol g^-1h^-1respectively.The photocatalytic performance of CQNU-1 as a bifunctional photocatalyst shows that the average H₂and O₂yields of CQNU-1 are 280?mol g^-1h^-1and 136?mol g^-1h^-1respectively in the presence of photocatalytic sacrifice agent.CQNU-1 is an excellent photocatalyst among all the IOHPs for photocatalytic total hydrolysis that have been reported in the literatures.2.Using 2,6-bis(4-pyridyl)naphthalene(Bpn)as the main ligand and SCN^-as the auxiliary ligand to react with inorganic metal ions,2 target IOHPs([Co(Bpn)₂(SCN)₂](6),[Ni(Bpn)₂(SCN)₂](7))were obtained.IOHPs 6 and 7 are isomorphic compounds,they both show two-dimensional layered structures.When IOHP 6 is used as a co-catalyst compounded on a Bi VO₄photoanode to form a 6/Bi VO₄electrode for the photoelectrocatalytic decomposition of aquatic oxygen,the 6/Bi VO₄electrode reveal a significant negative onset potential at 1.23 V vs RHE and a photocurrent density 3.7times higher than that of pure Bi VO₄.The mechanism study find that the improvement of oxygen production efficiency of 6/Bi VO₄may mainly attributed to the enhancement of water oxidation kinetics of 6/Bi VO₄and the enhancement of charge separation and transfer characteristic.