In Situ Formation Of 4-Cyanopyridinecarboxylic Acid And Its Polyacid Doping Supramolecular Compounds For Adsorption Of Organic Dyes In Wastewater

It is of great significance to design and synthesize new POMs-based inorganic-organic hybrid materials by using structural characteristics of polyoxometalates（POMs）to quickly and effectively remove pollutants in wastewater.In this paper,compounds 1-15 were synthesized using hydrothermal and room temperature volatile.Compounds 1-12 are new POMs-based inorganic-organic compounds based on organic cation ligands,transition metal compounds and polyoxometalates（POMs）,which have been synthesized in situ via coordination bonds and supramolecular self-assembly interaction at different p H.There are{[Cu·L1’·H₂O]·(α-Mo₈O₂₆)_0.5}_n（1）,{[Cu·L2’·H₂O]·(α-Mo₈O₂₆)_0.5}_n（2）,{[Cu·L3’·H₂O]·(α-Mo₈O₂₆)_0.5·H₂O}_n（3）,{[Cu·L4’·H₂O]·(α-Mo₈O₂₆)_0.5·H₂O}_n（4）,{[Cu·L5’·H₂O]·(α-Mo₈O₂₆)_0.5}_n（5）,{[Cu·L2’·（4,4’-b Py）₂·2H₂O]·(β-Mo₈O₂₆)}_n（6）,{[Cu·L4’·（4,4’-b Py）]·[Cu·L4’·(β-Mo₈O₂₆)·2H₂O]}_n（7）,{[Cu·L6’·H₂O]·(β-Mo₈O₂₆)_0.5·5H₂O}_n（8）,{[Cu·L7’·H₂O]·(β-Mo₈O₂₆)_0.5}_n（9）,{[L2’]₂·(α-Mo₈O₂₆)}（10）,{[L3’]₂·(α-Mo₈O₂₆)}（11）和{[L7’]₂·(β-Mo₈O₂₆)·2H₂O}（12）.Structural analysis of compounds 1-12 shows that increasing ligand conjugate surface,such as the addition of benzyl or rigid 4,4’-bipyridine auxiliary ligand,the coordination types of the polyacid anion were changed from[α-Mo₈O₂₆]^4-to[β-Mo₈O₂₆]^4-,the coordination mode of Cu was changed from dinuclear to mononuclear,and the structure type of compounds was changed from 2D to 1D or 3D.The basic characterization of compounds 1-12 was performed by IR,elemental analysis,UV-Vis,PXRD and single crystal X-ray diffractions.Compounds 1-12 have been studied for removal of organic dyes such as methylene blue（MB）,methyl orange（MO）and rhodamine B（Rh B）.We exhibited the adsorption mechanism,influencing factors and maximum adsorption capacity of compound 4 for MB adsorption.Compounds 13-15 are synthesized by self-assembly of branched cationic ligands with Bi I₃ and Cu I at room temperature.There are{[(C₂₀H₃₈N₂)₃·（Bi₂I₉）₂]·2CH₃CN}（13）,{[(C₂₀H₃₈N₂)₃·（Bi₂I₉）₂]·2CH₃CN}（14）and{[(C₂₀H₃₈N₂)·（Cu I₃）]}（15）.Among them,13 and 14 are dinuclear supramolecular compounds,and 15 is mononuclear supramolecular compound.The structure and properties of compounds 13-15 were investigated using a variety of characterization methods.Meanwhile,the adsorption properties and influence conditions of compounds 13-15 were studied.The experimental results show that compounds 1-12 have significant adsorption effect on cationic organic dyes,while compound 4 has a high adsorption capacity for MB.Therefore,the studying of compound 4 was chosen to understand the adsorption mechanism.By studying the adsorption mechanism of compound 4 against MB,it was found that the adsorption of compound 4 belongs to quasi-first order kinetic model and the Langmuir isotherms model,suggesting that the adsorption occurs on surface by monolayer sorption.Moreover,changing p H,temperature and the concentrations of salt solution,confirmed that the adsorption of compound 4 against MB belongs to exothermic reaction,and acidic solutions or salt solutions can promote the adsorption.In the adsorption performance test,we intuitively see that compounds13-14 have better adsorption effect on cationic organic dyes MB and Rh B,and compound 15 has a relatively better adsorption capacity on cationic organic dye MB.The adsorption effect of the compounds 13-15 on the organic dye MO is not obvious.