Design,Synthesis And Fluorescence Properties Of Chiral Metal-Organic Frameworks Based On Carboxylates Of Cyclohexane Diamide

Chiral luminescent metal organic frameworks as the new type of porous crystal material,have attracted widespread concern among researchers due to their potential applications in filds such as the enantioselective sensing and separation,solid state lighting,3D display,and information storage etc.In this paper,a series of chiral organic ligands,carboxylates of cyclohexane diamide were designed and synthesized.Subsequently,7 chiral MOFs with novel structure were synthesized by these chiral ligand with Zn salts,which were characterized and analyzed.More importantly,their luminescence properties were in detail explored.The main research work was as follows:1.The strategy of changing the coordination number and conjugation degree of the organic ligand in MOFs was proposed,by which the chiral MOFs with different photoluminescence properties were obtained.Carboxylates of cyclohexane diamide as ligands were designed and synthesized,including the reported semi-rigid tetracarboxylic acid ligands 5,5′-（（1R,2R）-cyclohexane dicarbonyl bis（azanediyl））diisophthalic acid（R,R-CHCAIP）and dicarboxylic acid ligands 4,4’-（1R,2R）-cyclohexanediamamide dibenzoic acid（R,R-CHCA）/4,4’-（（（1S,2S）-cyclohexanediamamide dibenzoic acid（S,S-CHCA）and the new semi-rigid conjugated tetracarboxylic acid ligands 4′,4?-（1S,2S）-cyclohexanediamido）dibenzoic acid（S,S-CHCA）and the new semi-rigid conjugated tetracarboxylic acid ligands 4’,4?-（（1R,2R）-cyclohexanenediacidyl））-two-（1,1’-biphenyl）-3,5-dimethic acid)（R,R-CCAPA）and 4’,4?-（（1S,2S）-cyclohexanenediacidyl）)-two-（1,1’-biphenyl）-3,5-dimethic acid)（S,S-CCAPA）,and also the enantiomeric 5,5′-（（1S,2S）-cyclohexane dicarbonyl bis（azanediyl））diisophthalic acid（S,S-CHCAIP）of R,R-CHCAIP were newly synthesized,and the three pairs of enantiotopic chiral MOFs,including M-HMOF-3/P-HMOF-3,M-HMOF-5/P-HMOF-5 and M-HMOF-6/P-HMOF-6 were synthesized by using three pairs of enantiotopic ligands as the main ligands with Zn²⁺.Under the strategy,the photoluminescence color of chiral Zn-MOFs was successfully modulated,showing a change from blue,cyan to yellow light.2.Based on the first research work（1）,the strategy of adjusting the auxiliary ligands in MOFs was raised,and chiral MOFs with different photoluminescence properties were obtained by using the identical main ligands（semi-righteous conjugate ligand R,R-CCAPA and S,S-CCAPA）and different auxiliary ligands.So,three pairs of MOFs,including M-HMOF-6/P-HMOF-6,M-HMOF-7/P-HMOF-7 and M-HMOF-8/P-HMOF-8 are constructed by selecting two-linked 4,4’-bipyridine（4,4’-bipy）,chelated coordination 1,10-Phenanthroline（1,10-Phen）and single-connected pyridine（Py）as the auxiliary ligand,and the light-emitting color shows significant changes,from blue light,green light to yellow light.Furthermore,the solid state M-HMOF-6/P-HMOF-6 shows the circularly polarized light.3.M-HMOF-6/P-HMOF-6,owning the 2D wave-like layer,showed good thermalstability and solventstability,high specific surface area,polymeric chiral environment and the number of exposed functional sites on the surface.The fluorescence sensing of HMOF-6 acetonitrile emulsion for unmodified D-/L-amino acid enantiomers was further explored.The detection results indicated that these enantiomers significantly quenching the photoluminescence of M-HMOF-6/P-HMOF-6 acetonitrile emulsions.More importantly,the emulsions showed good probed and enantioselective recognition for D-/L-amino acids andα-hydroxycarboxylic acids.In particular,L-lactic acid displayed high enantioselectivity that quenching ratio of M-HMOF-6/P-HMOF-6 K（L-lactic acid/M-HMOF-6）/K（L-lactic acid/P-HMOF-6）was 20.