酰胺类溶剂在合成MIL-101(Cr)中的作用

Effects of amide solvent on the synthesis of MIL-101(Cr)

在现有制备MIL-101(Cr)的过程中需有复杂的后处理纯化步骤,原料不能被充分利用。为了简化后处理过程,本文采用水热法合成MIL-101(Cr),并根据对苯二甲酸易溶于酰胺类溶剂的特点,在合成过程中分别加入适量的酰胺类溶剂N,N-二甲基乙酰胺(DMAC)、N,N-二甲基丙烯酰胺(DMAA)和N,N-二甲基甲酰胺(DMF),考察酰胺类溶剂对合成的影响。采用X线衍射仪(XRD)、N2吸附测定、扫描电子显微镜(SEM)等对添加酰胺类溶剂后合成的MIL-101(Cr)进行表征。结果表明:在合成过程中按照最佳摩尔比(n(对苯二甲酸)∶n(Cr(NO3)3·9H2O)∶n(溶剂)∶n(水)=1∶1∶0.3∶600)加入酰胺类溶剂,产物中不含有原料对苯二甲酸;添加DMF合成的MIL-101(Cr)具有清晰的孔径为0.96 nm的微孔和2.5、3.4 nm的介孔,其BET比表面积达到3601 m^2/g,总孔容为1.74 cm^3/g,样品形貌规整,晶体有完整的正八面体结构。添加DMF合成的MIL-101(Cr)结晶度高,无需后处理步骤,为批量化合成MIL-101(Cr)打下理论基础。

The synthesis of MIL-101(Cr)requires a complicated subsquent purification process which will cause the inefficient use of raw materials.Effects of amide solvents on hydrothermal synthesis of MIL-101(Cr)were investigated by adding an appropriate amount of N,N-dimethylacetamide(DMAC),N,N-dimethylformamide(DMF)and N,N-dimethylacrylamide(DMAA),based on the fact that terephthalic acid could be easily dissolved in amide solvents.The product synthesized by adding amide solvents was characterized by X-ray diffraction(XRD),N2 adsorption and scanning electron microscope(SEM).Results showed that there was no terephthalic acid remained in the product when an appropriate amount of amide solvents(n(H2BDC)∶n(Cr(NO3)3·9H2O)∶n(solvent)∶n(H2O)=1∶1∶0.3∶600)was added during the synthesis.The MIL-101(Cr)synthesized by adding DMF with no purification had three kinds of pores:micropore of 0.96 nm and two mesopores of 2.5 and 3.4 nm.The BET surface area(SBET)was 3601 m^2/g and pore volume reached 1.74 cm^3/g.The crystal morphology of the product was regular and it had a complete octahedral structure.The MIL-101(Cr)synthesized by adding DMF had high crystallinity degree and did not require complex purification steps,which laid a foundamental basis for mass production.