Design,Synthesis And Properties Of Multifunctional Rare Earth Coordination Polymers

With the rapid development of global industrialization,the problem of water pollution is becoming more and more serious,which has seriously threatened the survival and health of human beings.In addition,the greenhouse effect is also a thorny issue,and issues such as global warming,ocean acidification,and severe weather caused by CO₂ accumulation have attracted widespread attention.Therefore,it is particularly important to design and develop multifunctional materials that can not only detect trace pollutants in water,but also fix CO₂ gas.Metal coordination polymers(CPs)have broad application prospects in recent years in adsorption,catalysis,fluorescence and magnetism due to their structural designability and functional diversity.In this paper,10 rare earth coordination polymers(Ln-CPs)were designed and synthesized by hydrothermal synthesis method using two aromatic tetracarboxylic acid ligands and rare earth metal salts.The elemental analysis,infrared spectroscopy and single crystal X-ray diffraction structure analysis were carried out,and the fluorescence properties and catalytic properties were studied according to their structural characteristics.The main research contents are as follows:1.Based on 4-(3,5-dicarboxyphenoxy)phthalic acid(H₄deta)ligands and different rare earth metal nitrates,five kinds of isomorphic three-dimensional structures were successfully synthesized by the hydrothermal synthesis method.Ln-CPs:{[Ln₃(deta)₂(DMF)₂(COOH)·2H₂O]·DMF·H₂O}_n(1-5).Wherein,Ln=Dy(1),Tb(2),Gd(3),Sm(4),Nd(5),DMF=N-N-dimethylformamide.The basic characterization and fluorescence sensing performance of CPs 1,2,4 were investigated.CPs 1,2,4 can be versatile,efficient,and highly selective for the detection of trace pollutants,aniline(ANI),nitrobenzene(NB),tetracycline(TC),and pyrimethamine(Pth)in water by fluorescence.Among them,when CP 4 detects ANI,there is a change in the ratio of two peaks,and the detection limit obtained is better than that of a single peak.Finally,the fluorescence sensing mechanism was studied by UV spectroscopy as an energy competition absorption mechanism(CA).2.Based on 5-(3,4-dicarboxyphenoxy)isophthalic acid(H₄dppa)ligands,five Ln-CPs were synthesized by hydrothermal synthesis:{[Ln(dppa)(H₂O)₂]·dima·H₂O·0.5O}_n(6-10),where Ln=Tb(6),Gd(7),Eu(8),Dy(9),Sm(10),dima=dimethylamine.These five Ln-CPs are all heterogeneous two-dimensional network structures.CPs 6,8 and 9 with excellent fluorescence sensing performance were screened out by fluorescence analysis,which can detect a variety of pollutants in(Pb²⁺,B₄O₇^2-,Cr₂O₇^2-,ANI,NB,TC,Pth)with high efficiency,high selectivity and high sensitivity.It makes up for the problem of single fluorescence detection and realizes multi-functional detection of pollutants in water.In particular,CP 6 not only sensitively detects Pb²⁺and B₄O₇^2-ions through a fluorescence enhancement mechanism based on the Ln-CPs sensor for the first time,but also can detect ANI by ratiometric fluorescence with a detection limit better than that of a single peak.In addition,the fluorescence detection mechanism was explored through experiments and theoretical calculations,which involved energy-competitive absorption(CA),photo-induced electron transfer(PET),and weak interactions between analytes and complexes.3.The CPs 1,2 based on trinuclear rare earth clusters not only have three-dimensional microporous structures,but also the four crystallographically independent rare earth ions are unsaturated octa-and nine-coordinates,respectively,which can be used as potential Lewis acid activities sites.It has the potential as an efficient heterogeneous catalyst for Lewis acid-catalyzed reactions.Under optimized conditions,CPs 1,2 exhibited excellent catalytic activity for CO₂ cycloaddition.Its excellent heterogeneous catalytic performance and recyclability were explored through thermal filtration and recyclability experiments.Finally,the possible mechanism is proposed.