| Lanthanide and some actinide metal elements have complex energy level structures and characteristic fluorescence emission.The luminescence of the lanthanide metal ion center often depends on the sensitization of the"Antenna Effect"of organic ligands,while the actinide metal element uranium often exists in the form of a linear O=U=O2+molecule,and the electron tranisition from 2p to 5f orbital in the molecule occurs when it receives ultraviolet light;Actinide Th4+easily forms a metal cluster similar to the Zr-cluster in Zr-MOFs,and its extranuclear 5f,6d,and 7s orbital electrons can all bonding,form primary building units(PBUs)with larger coordination number(CN=4-15),and will form thorium-based fluorescent MOFs after coordination with luminescent organic ligands.At present,lanthanide/actinide metal-organic framework materials are widely used in heavy metal recognition,organic pollutant monitoring,radiation detection and other fields.In this paper,we used Tb3+and Th4+as metal centers to interact with4,4',4",4?-Methanetetrayltetrabenzoic acid(H4MTB)and tris(4'-carboxybenzidine)amine(H3TCBPA)organic ligands synthesized two novel MOFs under solvothermal conditions,and applied to the fluorescence recognition and enrichment studies of UO22+and IO3-,respectively.In addition,the synthesis and new applications of hydrogen-bonded organic framework materials were explored.Under the condition of room temperature volatilization,a hydrogen-bonded organic framework material with fluorescence was synthesized by using H4ADIP organic ligands,which can selectively identify trace amounts of D2O in water.The specific research results are as follows:1.[Tb4(C29O8H17)2(NO3)4(DMF)4(H2O)4]·4H2O·8.5DMF(YTU-100)was successfully constructed by using Tb(NO3)3·6H2O and 4,4',4",4?-methanetetrayl tetrabenzoic acid(H4MTB)under solvothermal method,with a high luminescence intensity.There are extremely high sensitivity and fluorescence selectivity to UO22+.The detection limits were as low as 1.07 ppb and 0.75 ppb in deionized water and tap water,respectively,as far as the U.S.Environmental Protection Agency(EPA)standard for uranium in drinking water of 30 ppb.This strong fluorescence response originates from the pore channel abundant functional groups and strong interaction with the guest molecule UO22+,when exposed to a low-concentration uranium solution,enrichment efficiency more than 90%can be achieved within 30 minutes,and the maximum adsorption capacity is 83.43 mg/g.The rapid adsorption behavior directly leads to the cut off of the energy transfer process between the organic ligands and the metal ions,which is finally shown as framework fluorescence quenching.2.Furthermore,we discovered a unique single-crystal-to-single-crystal(SC-SC)transition effect in actinide MOFs.Thorium often exists in the form of Th4+compounds,and the larger ionic radius is more conducive to the topological transformation of bond breaking and regeneration.C209H277N23Th6O85(Th-SINAP-200)can self-assemble into a hexanuclear thorium cluster MOF material with a double interpenetrating grid structure,which can exhibit triple single crystal to single crystal transition in organic solvent,water and Na IO3solution,Th-SINAP-201,Th-SINAP-202,and Th-SINAP-203,which became new conformations,crystallized in different space groups,respectively.The cationic properties of Th-SINAP-200 were calculated according to the framework charge balance and verified by experiments.It has extremely high sensitivity to anion IO3-,the limit of detection(LOD)is as low as 0.107?g/kg,and the maximum enrichment capacity for iodate reach 145.87 mg/g,which is the most sensitive material in the published iodate chemical sensor.3.Compared with metal-organic frameworks,have the advantages of dense hydrogen-bonded grids.We used 9.10-bis(3',5'-dicarboxyphenyl)anthracene(H4ADIP)and volatilized it in dimethyl sulfoxide(DMSO)solvent at room temperature to obtain a hydrogen-bonded organic frameworks(C30O8H18)(DMSO)4·0.5H2O(HOF-101)with strong fluorescence effect,which has a 3D mesh structure built with interactions such as hydrogen bonds,?-?bonds,etc.The strong fluorescence emission based on organic ligands can selectively identify microscale of D2O in water.It is also the first sensor that uses hydrogen bonding interaction to distinguish hydrogen isotopes. |
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