Application Of Stimuli-Responsive Infinite Coordination Polymers In Water Environment Monitoring And Treatment

Water eutrophication caused by nutrients such as nitrogen and phosphorus and water pollution caused by organic pollutants such as antibiotics will not only destroy the ecology,but also bring potential safety risks to human health.Therefore,it is of great significance for the water environment monitoring and control to select appropriate characterization factors to assess the eutrophication status and to adopt efficient processes to degrade emerging pollutants such as antibiotics.Infinite coordination polymers(ICPs)exhibit tunable composition and strong adaptability.In this paper,ICPs with different properties were synthesized by selecting appropriate guest molecules,central metals and organic ligands.Besides that,by taking advantage of their response to external stimulus,ICPs were used to realize the visual detection of alkaline phosphatase and the efficient photo-Fenton degradation of tetracycline hydrochloride in water.The detailed contents of this work are as followed:(1)The blue fluorescent dye 7-methoxy-3-carboxylic acid coumarin(7-MC-3-COOH)was selected as the guest molecule to regulate the coordination environment of the host lanthanide Eu-AMP ICPs and sensitize the red fluorescence of the Eu-AMP ICPs,which overcame the shortcomings that the fluorescence of traditional lanthanide ICPs is weak in water.At the same time,their blue fluorescence could also be used as an optical signal to construct the ratiometric fluorescent probe 7-MC-3-COOH@Eu-AMP ICPs.Based on the rupture of the 7-MC-3-COOH@Eu-AMP ICPs caused by the specific hydrolysis of P-O bond by alkaline phosphatase(ALP),the obvious fluorescence color from red to blue during the stimulation response was combined with the smartphone containing color recognition software to realize the on-site visual detection of ALP,and the detection limit was 0.0015 U m L^-1.Besides that,ALP could be used as an appropriate indicator of water eutrophication to serve for the early warning of algal blooms.(2)Bimetallic conductive Cu-(3,5-dbsq)(3,5-dbcat)-bix-Ag ICPs were synthesized using variable valence Cu(I)/(II)as metal ions,Ag as doping ions,electrochemically active 3,5-di-tert-butylcatechol(3,5-dbsq)(3,5-dbcat)and highly flexible 1,4-bis[(1H-imidazol-1-yl)methyl]benzene(bix)as ligands,which overcame the shortcomings of traditional ICPs that were not conductive.Based on the confinement effect of organic ligands and ICPs cavities on metal ions,the ultra-small Cu O_x-Ag₂O photo-Fenton catalysts were in situ synthesized on ITO glass by the stimulation response of ICPs to external current.In the presence of visible light,H₂O₂(10 m M)and Cu O_x-Ag₂O,the degradation efficiency of tetracycline hydrochloride(50mg/L)could reach 87.5%within 60 min,and the degradation efficiency was 72.4%after five cycles.This study not only provides a green and convenient method for the preparation of ultra-small size nanocatalysts,but also broadens the application of ICPs in materials science and environment fields.(3)To further improve the stability and catalytic activity of Cu O_x-Ag₂O,reduced graphene oxide(RGO)was selected as the carrier to synthesize the composite conductive Cu-(3,5-dbsq)(3,5-dbcat)-bix-Ag ICPs/RGO,which further improved the conductivity of ICPs.Similarly,ultra-small Cu O_x-Ag₂O-RGO photo-Fenton catalysts supported on ITO glass were prepared by electrochemical post-treatment strategy with Cu-Ag ICPs/RGO as the precursors.In the presence of visible light,H₂O₂(10 m M)and Cu O_x-Ag₂O-RGO,the degradation efficiency of tetracycline hydrochloride(50 mg/L)was 97.8%within 60 min.After five cycles,the degradation efficiency still reached91.4%.The results showed that the active substances in the photo-Fenton system were·OH,·O₂^-and h⁺.TC gradually mineralized to small molecular substances through functional group loss and ring-opening reaction,Cu O_x-Ag₂O-RGO was a Z-scheme heterostructure.This study not only provides a new strategy for the design,development and research of efficient photo-Fenton catalysts,but also provides a clear explanation for the degradation process of tetracycline hydrochloride.