| Porous materials,such as activated carbon,zeolites,mesoporous silica and so on,play an important role in production and human life.However,there are still some problems in the development of traditional porous materials,such as uncertainty of structure and difficulty of surface area breakthrough.In 1999,O.M.Yaghi Professor reported metal-organic frameworks(MOFs),named MOF-5,which attracted extensive attention of scientists.In the past two decades,scientists have carried out extensive research in the preparation of novel metal-organic frameworks and exploring various applications according to a set of well-established coordination chemistry theory.Compared to traditional porous materials,MOFs have the characteristics of high surface area,high design ability,adjustable and modified pore channels and so on,which make MOFs applied to adsorption and separation,heterogeneous catalysis,sensing,drug delivery,optics and other aspects.At present,the research work mainly includes two aspects.One is to improve the performance of synthesized MOFs by post-modification.The second is to focus on the synthesis of novel MOFs,and explore their properties and applications.This paper mainly focuses on the synthesis and properties of novel MOFs.The research work is as follows:(1)According to the method reported in literatures,we synthesized a four node carboxylic acid ligand(H4SFTBA)based on spirobifluorene.Three novel MOFs were synthesized with In(NO3)3,Mn Cl2·4H2O and Co(NO3)2·6H2O respectively,[(CH3)2NH2][In(SFTBA)]·(DMF)3.5·(H2O)3(compound1),Mn2O(SFTBA)(DMF)(H2O)n·(guest)x(compound2)and Co2O(SFTBA)(terminal)·(guest)x(compound 3)?Compound 1 was an anionic framework with open channel.Based on these excellent properties,we selected six kinds of organic dyes with different charges and sizes,including methylene blue(MLB),rhodamine B(RHB),neutral red(NR),sudan?(SD?),methyl orange(MO)and Orange?.Among them,MLB and RHB carry positive charges,NR and SD?are neutral,Orange II and MO have negative charges.The selective adsorption properties of compound 1 in DMF and ethanol solution were investigated,respectively.The results showed that compound 1 could selectively adsorb methylene blue(MLB),but excluded anionic dyes Orange II and MO as well as neutral dyes of NR and SD I in DMF solution.When the solvent environment was changed from DMF to ethanol,compound 1 could inhibit the cationic dye RHB and had obvious adsorption effect on both cationic dye MLB and neutral dye NR.The results indicated that the selective adsorption of organic dyes by compound 1 was mainly predominated by electrostatic interaction,size-exclusion effect and the solvent effect.Compound 2and 3 had the same structure,we took compound 2 as an example to analyze its structure.Compound 2 was a two-dimensional material with 4,4-c net and sql topology,and the Schl(?)fli symbol was[44·62].The metal cluster was similar to the dual-core Cu paddle-wheel,but due to the different coordination ability,it formed a disordered metal cluster with end-group solvent molecules.(2)An eight node carboxylic acid ligand(H8SFTTIA)based on spirobifluorene was designed and synthesized by Suzuki coupling reaction.Two novel MOFs were synthesized,which constructed from the organic ligand and Cu(NO3)2·3H2O and Mn Cl2·4H2O,namelyCu-SFTTIA(compound4)and Mn3.5(HSFTTIA)(H2O)x(DMF)y·(guest)n(compound 5),respectively.The crystal shape of compound 4 was rhomboid dodecahedron of typical cubic crystal system,but its crystal structure could not be determined because of twinning.We simulated two possible structures,noted as 4-simu a and 4-simu b.In these two structures,it could be considered that part of the metal center in HKUST-1 were replaced by the spirobifluorene,but the way of replacement was different.Compound4 was characterized by PXRD,TG,SEM,UV-Vis and elemental analysis.According to 77 K N2 adsorption test,the BET surface area of compound 4 was 828 m2 g-1,the main pore size was 5.4(?)and the pore volume was 0.375 cm3 g-1.The gas adsorption and separation properties of compound 4 for C1?C3 small molecular hydrocarbons were investigated.The results showed that the separation selectivities of C3H8/CH4and C2H6/CH4 for compound 4 were 1170 and 42 according to the ideal adsorbed solution theory(IAST)at 298 K and 1 bar,which were much higher than that of many reported MOFs.The results illustrated that compound 4 had good performance in CH4screening in light alkane separation.Compound 5 could be regarded as a 6,6-c three-dimensional network with the Schl(?)fli symbol[411·64].The calculation based on the PLATON software indicated that compound 5 had a total solvent accessible volume of 7191.6(?)3 per unit cell,accounting for about 45.8%of the cell volume. |
PDF Full Text Request