Preparation And Fluorescence Sensing Properties Of Dye-loaded Metal-organic Frameworks

Recently years,MOFs material has made significant contributions in various fields after raping development,and shown their unique advantages.The research tends to be saturated on the structure of MOFs materials,and the designed and synthesized MOFs structure has the expected properties.At present,there are still some thorny problems in some areas of MOFs.For example,when MOFs are used as sensors,they can not be better recognized by the naked eye.In the field of photochemical catalysis,the catalytic conversion and selectivity cannot meet the practical application require.In the field of drug delivery,accurate release of drugs cannot be achieved,etc.These issues need to be further explored.In this paper,two types of MOFs with different properties were constructed by solvothermal method,with different types of organic ligands.Based on the guest or ligand,the related properties of these two MOF materials were studied,and possible mechanisms were proposed.At the same time,their applications in the fields of photocatalysis and fluorescence sensing were explored.The specific research results are as follows:(1)Using in-situ synthesis method,the dye molecule Eosin Y was successfully loaded into DUT-52 composed of 2,6-naphthalenedicarboxylic acid and zirconium oxygen metal cluster,and a series of MOF compounds with dual-wavelength emission wre prepared,named EY@DUT-52.The EY@DUT-52 still maintains the original spatial structure of DUT-52,and its shape remains intact.Due to the good overlap between the absorption band of EY molecule and the emission band of DUT-52,energy transfer from DUT-52 to EY occurs in the compound of EY@DUT-52,which makes the compound of EY@DUT-52 present the luminescence characteristic of dual-wavelength emission.In view of the stable luminescence characteristics of EY@DUT-52,the relative peak height of the two peaks in the compound was used as the detection signal instead of the absolute peak height of the emission peak in the traditional test to detect 21 pesticide ethanol solutions.The results showed that the E@D1 and E@D3 compounds showed high selectivity and sensitivity for nitenpyram.The detection mechanism of E@D1 and E@D3 compounds were different.Due to the spectral overlap between the DUT-52-based luminous band and the absorption spectrum of nitenpyram,E@D1 directly exhibits fluorescence quenching during the detection process.However,for E@D3,the resonance energy transfer from DUT-52 to nitenpyram causes the energy transfer from DUT-52 to EY molecules to be restricted,showing fluorescence quenching.This research laid the foundation for the study of MOF materials in the field of self-calibrating fluorescent sensors.(2)A series of dye@MOF composites were synthesized through in situ encapsulating luminous RhB molecules into a blue-emissive zirconium-naphthalene based metal-organic framework(Zr-MOF).The fabricated RhB@Zr-MOF composites exhibit tunable dual-emissive characteristics due to the process of resonant energy transfer from Zr-MOF to RhB.Notably,one of RhB@Zr-MOF composites(R@D3)exhibited a weak emission at 420 nm and a strong emission at 607 nm where the two independent emissions possess large distinctions in location and intensity and can be referenced each other in sensing analytes.By using relative fluorescence intensity instead of their absolute fluorescence intensity as detection signals,R@D3 severed as a built-in self-calibrated platform to selectively detect Fe3+ and Cr2O72-ions in water.Compared with the pristine Zr-MOF,R@D3 composite shows enhanced sensing selectivity to Fe3+ and higher sensibility to Cr2O72-.This study displayed the advantages of combining organic dyes with robust Zr-MOF in tuning the fluorescence and sensing performance.