| Metal-organic polyhedra(MOPs)are another kind of porous material which develops rapidly after molecular sieve and metal-organic framework(MOFs).MOPs are discrete cage-like metal-organic molecular entities composed of metal ions or clusters and organic linkages,which have received widespread attention due to their fascinating structures and potential applications(e.g.,adsorption,catalysis,membranes,biomedical fields,etc.).Polyoxometalates have been successfully applied to the synthesis of organometallic polyhedra,the most common of which is the organometallic polyhedron with multimetal vanadyl clusters as building units.However,compared to vanadium-based MOPs,zirconium-based MOPs exhibit higher stability and their performance investigation in aqueous solutions has excellent prospects for application.In this paper,five zirconium-based organic polyhedra and one vanadium-based organic polyhedra were design synthesis by coordinating vanadium oxide sulfate and zirconium dichloride as metal centers with bidentate and tridentate carboxylic acid ligands,respectively,and MOPs materials with specific structures were obtained by adjusting the reaction temperature and the ratio of reaction solvent under the condition of solvothermal method.In particular,Zr-MOPs exhibited good water stability and were investigated as adsorbents for the adsorption performance of dyes and heavy metal ions in water bodies.(1)The synthesis of vanadium-based metal organic polyhedra adopts step-by-step synthesis strategy,the pre-polymer{V6S}was first prepared under solvothermal conditions using VOSO4 as the source of vanadium metal,and then the VMOP-TATB were constructed by coordination with the tridentate carboxylic acid-containing ligand H3TATB,whose the molecular formula of the compounds are:{V6O6(OCH3)9(SO4)4(TATB)4}·nDMADMA:N,N-DimethylacetamideTATB:1,3,5-triamino-2,4,6-trinitrobenzene(2)Two examples of zirconium-based metal-organic polyhedra with different spatial configurations were synthesized by solvent-directed strategy of zirconium dichlorodichloride with the linear bidentate carboxylic acid ligand H2NDC as the reaction material under solvothermal conditions.In addition,the adsorption properties of two Zr-MOPs on four kinds of dye molecules with different charges were investigated systematically.The results show that the two Zr-MOPs have adsorption effects on both anionic and cationic dyes.For Zr-MOP-1adsorbed dyes(MLB+and CV+),the pseudo-second-order kinetic model could well fit the adsorption kinetics,indicating that the adsorption process is mainly chemisorption;meanwhile,the Langmuir model could fit its adsorption isotherm data well,indicating that the process is unimolecular layer adsorption.For Zr-MOP-2 adsorption of dyes(MLB+and CV+),the pseudo-second-order kinetic model can better describe its adsorption behavior for both dyes;unlike the adsorbent Zr-MOP-1,the Freundlich isotherm is more correlated than the Langmuir and Tempkin isotherm models.In addition,the adsorption properties of Zr-MOP-2 for heavy metal anions(Cr(VI)and Mn O42-)were investigated and both were consistent with the pseudo-second-order kinetic model;the correlation of the Freundlich isotherm was higher than that of the Langmuir and Tempkin isotherms,indicating that the adsorption was not only for a single molecular layer.The adsorption performance of Zr-MOP-2 was also investigated for heavy metal(Cr(VI)?Mn O4-)ions in water under different conditions(p H,adsorbent dosing and interfering ions).The molecular formula of the compounds are:Zr-MOP-1:{[Cp3Zr3?3-O(?2-OH)3]4(NDC)6}·Cl4·(DMA)16.5·(H2O)40Zr-MOP-2:{[Cp3Zr3?3-O(?2-OH)3]2(NDC)3}·Cl2·(DMF)2·(H2O)1.5NDC:2,6-naphthalenedicarboxylic acidDMF:N,N-dimethylformamide(3)Based on the above experience,we chose H2EDB ligands with longer size as opposed to H2NDC to synthesize one-case Zr-MOP-3 under solvothermal conditions with a calculated cavity volume of 116.9?3.Afterwards,aliphatic ligands(FUM and AA)were chosen to self-assemble with 3-connected{Zr3}clusters to form two cases of capsule Zr-MOPs,namely Zr-MOP-4 and Zr-MOP-5.The molecular formula of the compounds are:Zr-MOP-3:{[Cp3Zr3?3-O(?2-OH)3]2(EDB)3}·Cl2Zr-MOP-4:{[Cp3Zr3?3-O(?2-OH)3]2(FUM)3}·Cl2Zr-MOP-5:{[Cp3Zr3?3-O(?2-OH)3]2(AA)3}·Cl2H2EDB:4,4'-(ethyne-1,2-diyl)dibenzoic acidFUM:Fumaric acidAA:Adipic acid... |
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