Metal-Organic Framework Of Pyridinealcohol-Carboxylate:Design,Synthesis And Sensing

As a new type of porous material,metal-organic framework(MOF)have a bright future in the gas adsorption,drug delivery,catalysis,magnetic and sensing areas.In view of its structure and aperture size is adjustable,therefore,designed synthesis MOF of specific functions has become particularly important.In recent years,the special ability of the pyridinealcohol ligand and the transition metals to form clusters attracted more researchers attention.It has been found that these pyridine alcohol clusters exhibit excellent properties in terms of magnetic properties and catalysis.In view of this,we are committed to introduce the diversified coordination of carboxylic acid functional groups into pyridine alcohol ligands,and designed synthesis a series of pyridine alcohol carboxylic acid ligands.Then,explore the reactivity of the pyridinealcohol-carboxylic acid ligand with transition metals and the subsequent physical and chemical properties of the relevant complexs.In this paper,we selected two kinds of pyridinealcohol-carboxylic acid/ester ligands(hydroxymethyl)pyridin-3-yl)isophthalic acid(H2L1)/dimethyl 5-(6-(hydroxymethyl)pyridin-3-yl)isophthalate(L2),and coordinated with the Cd and Zn salts to prepare a series of MOFs and monomolecular compounds.Analysis of the structure and properties of the compounds,and further explored the structural relationships between these compounds and their application in fluorescent probe.In this article,we describe a one-pot assembly of Cd(NO3)2·4H2O with 5-(6-(hydroxymethyl)pyridin-3-yl)isophthalic acid(H2L1)in DMF/H2O to afford a 2D MOF[Cd(L1)(H2O)2](A)and two 3D MOFs[Cd(L1)(DMF)0.5](B)and[Cd(L1)](C).MOF A consists of a Cd2 unit connected by a pair of aqua bridges.A trial of SCSC conversion by removing the aqua bridges in A,results in a new 3D MOF of[Cd(L1)](D),which is a polymorph of C.Investigating the preceding complex that can convert to A in water led us to isolate a 2D MOF[Cd(L1)(DMF)](E),prepared via the reaction of Cd(NO3)2·4H2O and H2L1 in DMF.Single crystals of E convert to A within a period of ca 2 h,but with the loss of single crystallinity.Compounds A,D and E are luminescent and A selectively detects Fe3+ in water at ppm levels in the presence of other cations.Finally,we also investigated the reactivity of H2L1/L2 with Zn salt,in which H2L1 and Zn salt produced a two-dimensional compound[Zn(L1)(DMF)](F)under evaporation at room temperature,and L2 with Zn salts yieled a monomolecular compounds[Zn(L2)(L3)(NO3)](G)under the solvothermal conditions.By analyzing its structure,we found that one of the alcoholic hydroxyl groups in the compounds G were oxidized to carboxylic acid.L2 and both compounds have strong fluorescence emission.