Synthesis And Properties Of Uranium Metal Organic Frameworks

Metal-organic frameworks?MOFs?are porous crystalline materials with regular structures formed by metal ions or metal clusters and organic ligands.They are widely used in gas adsorption and separation,chemical sensing,optical materials and multiphase catalysis and other fields.At present,MOFs based on transition or lanthanides elements have been widely reported,and their synthesis and properties have been extensively decumented.In conctrast,the study of MOFs based on actinides is relatively rare.Uranium is the representative of actinides.The linear makes its structure very rich.At the same time,the electronic configuration of uranyl determines its special optical,electrical,magnetic and catalytic properties.The study of the nature of the uranyl organic frameworks can further enrich the coordination chemistry of actinides,which is expected to realize the reuse of nuclear waste.This has important implications for today's lack of resources.Therefore,this paper selects uranium as a metal node and different carboxylic acid ligands to construct a series of new uranium organic frameworks?UOFs?,and their performance in fluorescence sensing were studied.The main research results of this paper are as follows:1.[?UO₂??H₂DTATC?]?HNU-39,H₄DTATC=5,5-?9,10-dihydroxy-4a,9,9a,10-tetrahydroanthracene-9,10-diyl?-diisophthalic acid?was synthesized using uranyl and 5,5?-?Anthracene-9,10-diyl?diisophthalic acid?H₄DPATC?under hydrothermal conditions.It is interesting that the ligand H₄DPATC undergoes an in situ reaction and was transformed into a hydroxyl-containing ligand H₄DTATC during HNU-39synthesis.In addition,HNU-39 does not have fluorescence,but it can be used as a“turn-on”sensor in the range of p H 9.4-11.5,and it has good recycling performance.The sensing mechanism can be explained as the acid-base neutralization reaction of OH^-ions with the protons on the carboxylic acid groups that are not involved in the coordination.In addition,HNU-39 has also been successfully applied to p H measurement of actual water samples in sewage treatment plants.This work provides the possibility to develop a potential p H-dependent uranium-based MOF fluorescent sensor,and also provides a new strategy for the research of MOFs fluorescent sensors containing protonated/deprotonated groups.2.[?UO₂?₄?U^V???-O?₆?H₂O?₄(C₂₀H₁₆N₂O₄)₂Cl]?HNU-46?with a triple interpenetrating structure of mixed uranium valence states was synthesized using the purple purine ligand 1,1'-?1,4-phenylene-bis?methylene??-bis?pyridine-4-carboxylic aicd??L2?and uranyl.Its crystal structure contains U?VI?and U?V?ions.It is very rare for UO₂²⁺cations to change from U???to U?V?during synthesis.This method provides a strategy for fixing unstable U?V?and provides a new idea for the treatment of uranium waste.In addition,HNU-46 can achieve"turn-on"of fluorescence at low temperature,and the fluorescence intensity is related to temperature,which can be used as a temperature sensor in the low temperature region.3.[?UO₂?₃?H₂O?₂?HTCPE?₂]·2H₂O?HNU-47?with 3D structure was synthesized using aggregation-induced fluorescence effect ?AIE?ligand 1,1,2,2-Tetra?4 An example of the synthesis of-carboxylp-henyl?ethylene?H₄TCPE?and uranyl.Interestingly,three of the four"rotor"rings of the benzene ring of the ligand in HNU-47 cannot be rotated by carboxylic acid and uranyl coordination,and the other"rotor"is not coordinated with a protonated carboxylic acid group.Taking advantage of the carboxylic acid's ability to easily form hydrogen bonds,the acetic acid molecule was detected,and it was found that the acetic acid molecule was enough to enable HNU-47 to turn on fluorescence.This is because the acetic acid molecule and the protonated carboxylic acid form a hydrogen bond,making the"rotor"unable to rotate,which leads to the AIE effect.The detection of acetic acid molecules can be used to detect the content of acetic acid in the production and storage of fruit wine,which has potential utilization value in the production process of fruit wine.