| Due to structural diversity,adjustability,modularity and multiple intermolecule interactions between frameworks and guest species,zinc and cadmium organic frameworks are regarded as a promising luminescence sensing materials.The challenge is to improve the chemical stability of this materials and illustrate the relationship between intermolecule interactions and target species,and realize the sensitive and quick detection.Guided by supramolecular self-assembly strategy and coordination chemistry principle,two supramolecular organic frameworks and nineteen zinc and cadmium metal organic frameworks were synthesized by varying substituted groups of benzoic acid ligands as main ligands from monocyclic dicarboxyl,dicyclic dicarboxyl,tricyclic dicarboxyl,pyridinic carboxyl to pyrazo pyrazine.The aim of changing substituted units of multi-terminal carboxyl ligands to regulate and functionalize frameworks was realized.The crystalline structures were characterized by IR spectra,X-ray diffraction.And sensing performances were tested by UV-vis and luminescence spectra to investigate the effect of weak interactions on conformation and packing form of ligands and the relationship between structure and sensing performance.Based on the knowledge of hydrogen bond interaction,two supramolecular organic frameworks were synthesized,[?H2bpdc?0.5?4,4?-bipy?0.5]?1?and [?H3dpob??4,4?-bipy?·3H2O]?2?.By increasing ratio of metal salts and p H value,five metal organic frameworks {[Cd?Hdpob??H2O?3]·H2O}n?3?,[Cd?Hdpob??bib?]n?4?,[Zn?Hdpob??bib?0.5]n?5?,{[Cd1.5?dpob??2,2?-bipy?]·0.5H2O}2n?6?and {[Cd3?dpob?2?4,4?-bipy?2]·3H2O}n?7?,were designed based on 3-?2?,3?-dicarboxyl phenoxy?benzoic acid?H3dpob?.The different conformations of 4,4?-bipy induced by weak noncovalent interactions are responsible for diverse aggregation-induced emission activity between 1 and 2.Dual-emissions in DMSO solvent of compounds 3-7 were observed.Remarkably,emissions of 4 and 5 with same ligands and similar structures can be tuned between blue and green in opposite directions by varying excitation.Tris-?carboxylphenyl?phosphine oxide?H3tpo?is chosen to synthesize two metal organic frameworks,{[Zn?Htpo?]·6H2O}n?8?and {H[Zn3?OH??tpo?2]·3DMF·2H2O}n?9?by increasing conjuation and symmetry of substituted unit of benzoic acid.Under the guidence of topological analysis,{[Cd1.5?tpo??4,4?-bipy?1.5]·3H2O}2n?10?is obtained.Compound 10 shows a sensitive detection and reusability to TNP.Moreover,the high stability of 10 in organic solvents and acid/base solutions has been systematically discussed and explained in terms of structural robustness and kinetic inertness.After consideration of conjuation and flexibility of substituted units of ligand,two metal organic frameworks are constructed from 1,3,5-tri?4-carboxyphenoxy?benzene?H3tcpb?,H[Zn3?OH??tcpb?2?H2O?3]·3H2O?11?and H[Zn3?OH??tcpb?2?DMA?]·DMA·4H2O?12?.“Six leaf windmill” shaped 11 exhibits notable emission enhancement and red-shift toward DMA,during which structural transformation occus due to ?2-bridging H2O release,DMA coordination and conformational change of ligand.Compound 12 reveals high selectivity and effective naked eye recognition for Co2+ ions thanks to the dynamic and static quenching mechanisms.Detection limit?LOD?was 0.22 ?mol/L.Subsequently,by changing one carboxyl into pyridine as substitution,six metal organic frameworks have been synthesized based on 5-?4?-carboxylphenyl?nicotinic acid?H2cpn?and 5-?4?-carboxylphenoxy?nicotinic acid?H2cpon?,[Cd?Hcpn?·Cl·CH3OH]n?13?,[Cd?cpn?·H2O]n?14?,{[Cd2?cpon?2·2H2O]·H2O}n?15?,[Cd?cpon?·2H2O]n?16?,[Zn?cpon?·H2O]n?17?and [Zn?cpon?]n?18?.Combining the flexibility and dynamic of framework,4-?4-diethylamino styryl?-1-methylpyridinium?DEASM?as gust is successfully encapsulated into 16.The resulting composite displays the dual-emission behavior with the color linearly tuned from green to red and ratiometric luminescent in response to pH change.Furthermore,composite exhibits sensitive sensing performance to nitrofurazone and could be integrated into a logic operation.By continuously replacing the other substituted carboxyl by multiazole group,1-?4-carboxylbenzyl?-3-?pyrzin-2-yl?pyrazole?Hcpp?is chosen to synthesize three metal organic frameworks,[Cd?cpp??ac?·H2O]?19?,{[Cd?cpp??Hdcb?·H2O]·H2O}?20?and {[Cd?cpp??tdc?0.5·H2O]·3H2O}n?21?by controlling the bridging angle of the ditopic ligand.Eu3+ is anchored within the framework of 21 to form a dualemmisive composites Eu3+@21 successfully because of the abundant potential active sites.The composite shows a sensitive?LOD was 6.74 nmol/L?and selective response toward dipicolinic acid?DPA?,a anthrax biomarker,stemmed from cosensitization and preferential coordination. |
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