Stimuli-responsive Luminescent Metal-organic Frameworks:the Designed Syntheses And Applications

Stimuli-responsive luminescence materials hold promising characteristics for generating photofluorescence emission transfer along with external stimuli(e.g.light,pressure,temperature,humidity,pH value,electric field,magnetic field and organic analytes),showing a great potential for the applications in mechanosensors,chemical sensors,biological sensors,storage devices,switches,light-emitting devices and so on.Of the large variety of such materials candidates,luminescent metal-organic frameworks(LMOFs)stand out from peers owing to their highly tunable luminescence and structural diversity.Moreover,the definite crystalline structures of LMOFs provide their exact structural information,promoting the in-depth study on the mechanisms of the stimuli-responsive luminescence behavior.All these together make LMOFs a perfect platform for the synthesis and characterization of stimuli-responsive luminescence materials.In this thesis,three new LMOFs materials with stimuli-responsive luminescence function were constructed by different synthesis strategies,and their luminescent mechanism and properties were studied and explored.The main research contents are as follows:1.A stable nanoscaled single-excitation ratiometric luminescent pH sensor(MPDB-PCN)was synthesized by simple and effective post-synthetic modification of PCN-224 with a naphthalimide-derived functional molecule.As a stable nanoscale pH sensor,MPDB-PCN can detect pH values rapidly,sensitively and reversibly across a broad range from acid to basic pH range(2.5-8.6).Furthermore,the single-excitation detecting pattern and amplified ratiometric output make MPDB-PCN capable for real-time pH detection in complicated environments.Moreover,we explored its detecting capability for toxic mycotoxin(3-Nitropropionic acid,3-NPA)in a complicated sugarcane environment,and found that it also exhibits a highly sensitive detection regarding with limit of detection(LOD)=15?M.2.Co-ETTB with complete non-emission(?_F=0.14%)was synthesized by using an aggregation-induced emission(AIE)organic chromophore(H₈ETTB)as organic ligand and Co(?)as metal node.In addition,non-emission Co-ETTB exhibits a turn-on fluorescent enhancement under the stimulation of analyte histidine(His),which was due to linkers in the MOFs are released through competitive coordination substitution and subsequently reassembled to perform aggregation-induced luminescence behavior originated from the organic linkers.Based on this turn-on fluorescent enhancement behavior,Co-ETTB has become a sensitive histidine fluorescence sensor with LOD=11?M.Furthermore,to probe the trace of His in a convenient and rapid manner,portable Co-ETTB-deposited test strips were prepared for practical tests with a minimum detection concentration as low as 5?M that can be observed through the naked eye.3.Sr-ETTB with strong blue fluorescence(?_F=54.6%)was synthesized through using different outer shell electron configurations of Sr(II)with the above AIE type organic ligand.By changing the tunable luminescence performance of metal nodes,the fluorescence intensity of the MOFs is tuned from complete non-emission to high emission,which provides a good idea for the design and synthesis of LMOFs in the future.More interestingly,Sr-ETTB exhibits rare reversible thermal/piezoelectric fluorescence and thermochromic/piezoelectric behavior,which is driven by its unique flexibility of crystal structure.These results also provide a new perspective for the design and preparation of stimulus-responsive luminescent materials.