Metal Orginc Framework-based Luminescent Composites:Preparation And Applications

Metal organic frameworks?MOFs?have potential applications in optics,catalysis,sensing,drug delivery and selective adsorption and separation,and have become one of the hot research topics.Among them,MOF composite luminescent materials have attracted great attention.The luminescence properties of MOF composite luminescent materials,mainly from the ligand luminescence,charge transfer luminescence,guest luminescence and metal ion luminescence,etc.Due to the diversity of their luminescent properties,a large number of MOF composite luminescent materials have been reported and widely used,such as chemical sensing,white luminescent materials,second-order nonlinear optical materials,drug delivery and biological imaging.According to the MOF tunnel shape and size can be adjusted to give them the ability to load the optical functional guest into the channel.Based on this viewpoint,the preparation and applications of MOF composite luminescent materials are carried out in this thesis.The related detailed studies were stated as follows:1.A lanthanide functionalized MOF hybrid for ratiometric luminescent detection of an anthrax biomarkerIn this thesis,Dipicolinic acid?DPA?can serve as a convenient biomarker for Bacillus anthracis,which is an extremely hazardous disease and can be used as a biological weapon.Herein,we demonstrates a ratiometric fluorescent sensor of DPA based on a dual-emissive MOF hybrid,which is developed by encapsulation of Tb³⁺cations into a anionic MOF through a cation exchange process.The Tb³⁺@MOF hybrid well inherits the intrinsic ligand emission of host framework and the Tb³⁺emission.The parented framework can function as a host matrix to sensitize and protect the emission of incorporated Tb³⁺.The Tb³⁺emission within MOF hybrid significantly enhances in the presence of DPA molecules owing to the occurrence of antenna sensitization upon formation of Tb-DPA complex,while the ligand emission within the hybrid is insensitive to DPA.This unique ratiometric luminescence response of Tb³⁺@MOF hybrid towards DPA can be exploited for sensitive self-calibrated detection of DPA.The Tb³⁺@MOF sensor shows fast response rate,high sensitivity and selectivity with a limit of detection of 3.6 nM.Besides,the feasibility of this sensor operating in real samples is demonstrated by the good recovery of DPA in human serum.Present study provides a promising luminescent platform for routine analysis of an anthrax biomarker.2.A luminescent Lanthanide-free MOF nanohybrid for highly sensitive ratiometric temperature sensing in physiological rangeLuminescent MOF materials with tunable emissions and energy/charge transfer processes have been extensively explored as ratiometric temperature sensors.However,most of the ratiometric MOF thermometers reported thus far are based on the MOFs containing photoactive lanthanides.Here,we present a ratiometric luminescent thermometer based on a dual-emitting lanthanide-free MOF hybrid,which is developed by encapsulation of a fluorescent dye into a robust nanocrystalline zirconium-based MOF through a one-pot synthesis approach.The pore confinement effect well isolates the guest dye molecules and therefore suppresses the nonradiative energy transfer process between dye molecules.The incorporated dye emission is mainly sensitized by the organic linkers within MOF through fluorescence resonance energy transfer.The ratiometric luminescence of the MOF hybrid shows a significant response to temperature due to the thermal-related back energy transfer process from dye molecules and organic linkers,thus can be exploited for self-calibrated temperature sensing.By integrating the advantages of excellent stability,nanoscale nature,and high sensitivity and precision in the physiological temperature range,this dye@MOF hybrid might have potential application in biomedical diagnosis.What'more,this work has expanded the possibility of non-lanthanide luminescent MOF materials for the development of ratiometric temperature sensors.3.Nanoconfinement of all-inorganic Cesium Perovskite quantum dots in a mesoporous MOF:space-confined synthesis,enhanced stability and luminescence propertiesAlthough the properties of perovskite nanocrystals?NCs?have been extensively studied,the perovskite quantum dots?PQDs?suffer from poor stability due to their high sensitivity to air moisture,making their synthesis challenging.Here we demonstrate a simple method to grow CsPbX3?X=Br,I?quantum dots.The CsPbX3 precursor solution is formed by the addition of CsX and PbX2,which are dissolved in dimethylsulfoxide?DMSO?solvent.Then,the precursor is introduced into the mesoporous MOF HP-UiO-66.And the size of the CsPbX₃ quantum dots is confined by the pore size of the MOF templates?5 nm?.Photoluminescence measurements of CsPbI₃ quantum dots clearly shown that quantum dots grown in the MOF pores have a blue shift of 9 nm compared with the same conditions to grown simple PQDs,owing to the oriented porous MOF materials.At the same time,photostability tests show that CsPbX₃ samples encapsulated in MOF are obviously stable than non-encapsulated CsPbX₃ NCs.This strategy of confined growth of perovskite quantum dots suggests that perovskite NCs loaded in tunable MOFs will passivate their sensitivity to air and form new optical properites.The method provides a new way to improve the stability of perovskite quantum dots in the air.