| In recent years,the development of science,technology and industry has not only promoted social progress,but also brought many negative effects to our living environment.Therefore,it is urgent to solve the increasingly serious environmental pollution.With the rise of various industries and light industries,the discharge of industrial wastewater containing a large number of pollutants not only causes serious water pollution,damages the balance of the ecosystem,and even endangers human health.Therefore,sensitive detection and efficient removal of pollutants in the water environment have become the focus of current researchers.At present,the development of porous materials provides theoretical basis and technical support for solving the problem of water environmental pollution.Metal-Organic Frameworks(MOFs)is a multi-dimensional crystal hybrid material constructed from organic ligands connecting metal nodes/clusters,which has become new multifunctional material.MOFs materials not only have large specific surface area,porous properties and high crystallinity,but also have regular arrangement and dense adsorption active sites inside the pores,which make them have wide application prospect in the fields of gas storage and separation,proton conduction,chemical sensing,magnetic and heterogeneous catalysis.Starting from improving and enhancing the performance of MOFs material,by taking multi-nitrogen heterocyclic ligands and organic carboxylic acid ligands as building blocks,combining with different metal salts,we design and construct a series of new efficient and stable MOFs through adjusting the synthesis method,reaction conditions and surface morphology characteristics of materials in this paper.MOFs materials with appropriate pore size were screened out,the crystal phase,structure and composition of these materials were analyzed in detail,and studies on photocatalytic degradation,sensitive detection and selective adsorption and separation of pollutants(organic dyes,metal ions and nitroaromatic compounds)in the environment were carried out.The main results of this paper are as follows:(1)Four new MOFs,namely,[Zn2L]n(1),[Mn(H2L)(H2O)]n(2),[Cd(H2L)(H2O)2]n·n H2O(3)and[Pb2L(H2O)]n·3n H2O·n DMF(4),have been prepared by using a tetracarboxylic acid ligand H4L(H4L=5-(bis(4-carboxybenzyl)amino)isophthalic acid)under solvothermal conditions and structurally characterized by elemental analysis,IR spectroscopy,single-crystal X-ray diffraction analysis and powder X-ray diffraction.Structural analyses reveal that 1,2and 4 exhibit three-dimensional network structures.The structure of 1 can be symbolized as a 2-nodal 6-connected net with(411·64)(47·68)topology.The framework of 2 can be considered as a 4-connected net with(62·84)(63·83)topology.The structure of 4 can be regarded as a 5-connected net with a 43·66·8 topology.In contrast,3 exhibits 2D structure with 3,3-connected(63)2topology.The thermal stabilities and gas adsorption properties of 1-4 were studied.The experimental results show that 1-4 have good thermal stabilities and selective adsorption properties for CO2.Besides,the photocatalytic properties of 1-4 under visible light irradiation were studied.The results show that complex 1 has good photocatalytic degradation efficiency on methylene blue(MB).(2)Three new MOFs,namely,[Cu2(2-NCP)2(H2N-bpdc)]n(5),[Pb2(2-NCP)2(H2N-bpdc)]n(6)and[Cd(3-NCP)2]n(7),have been prepared by using N-and O-donor ligands 2-HNCP,3-HNCP and H2N-H2bpdc(2-HNCP=2-(2-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline,3-HNCP=2-(3-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline,H2N-H2bpdc=H2N-biphenyldicarboxylic acid)and metal ions Cu2+,Pb2+and Cd2+under hydrothermal conditions.The single-crystal X-ray diffraction analysis was used to measure the crystal structure.The complexes 5 and 7 are one-dimensional chain structures,they can further form two-dimensional and three-dimensional supramolecular structures through?-?stacking.The complex 6 is a two-dimensional layered structure,which can form three-dimensional supramolecular structure through?-?stacking.The fluorescence detection performance for small molecular solvents and metal ions of the new fluorescent complex constructed by transition metal Cd2+ions with d10 structure were investigated.The results show that the complex 7 could quickly detect nitrobenzene and Fe3+by fluorescence quenching,and had good anti-interference and cycle stability,so it was a potential chemical fluorescence sensing material.(3)Three multifunctional fluorescent MOFs,namely,[Eu(4-NCP)(1,4-bdc)]n·0.5H2O(8)?[Tb(4-NCP)(1,4-bdc)]n·2H2O(9)and[Eu(4-NCP)(4,4'-bpdc)]n·0.75H2O(10)(HNCP=2-(4-carboxyphenyl)imidazo(4,5-f)-(1,10)phenanthroline,1,4-H2bdc=benzene-1,4-dicarboxylic acid,4,4'-H2bpdc=4,4'-biphenyldicarboxylic acid)have been hydrothermally synthesized and characterized via elemental analysis,infrared spectrometry and single crystal X-ray diffraction.Structural analyses reveal that three complexes all exhibit three-dimensional network structures with a Schl?fli symbol of412·63 topologies.Besides,these three MOFs present excellent thermal stabilities and the preferential adsorption of CO2 over N2.In addition,the complex 10 was used to study the fluorescence sensing properties of metal ions and nitro aromatic compounds.The results show that both metal ions and nitro aromatic compounds can quench the fluorescence intensity of complex 10 in varying degrees.Among them,Fe3+and nitrobenzene showed the most obvious quenching phenomena,and they have good anti-interference and recycling properties,so complex 10 can be used for detection of complex components.(4)Cu2O was used as the template to form the core-shell structure of Cu2O@HKUST-1 by in situ growth technology.By further removing the template,the cavity structure was successfully introduced into the aggregate to form the hollow structure wrapped in HKUST-1,which is called HKUST-1 Shell.The adsorption experiments show that HKUST-1 Shell has a good adsorption effect on nitrobenzene pollutants in wastewater.Through the investigation of various factors affecting the adsorption,the adsorption equilibrium can be reached within 40 min,and the adsorption amount shows a linear growth trend with the increase of solution mass concentration.Using the adsorption isotherm and kinetic equation fitting experimental results,we can know that the adsorption ability of HKUST-1 Shell to nitrobenzene is in good agreement with Freundlich model,indicating that the adsorption form is heterogeneous adsorption in the hole of HKUST-1 Shell.The adsorption process conforms to the second-order kinetic model,which indicates that the adsorption kinetics is mainly controlled by chemical action. |
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