摘要/Abstract

选用2，5-二甲氧基对苯二甲醛和四胺基四苯甲烷利用溶剂热的方法在反应釜中制备得到一种新型的含有醚氧基团的3D共价有机骨架（DMTA-COF）.通过理论模拟，粉末X射线衍射（PXRD）、傅里叶变换红外光谱（FT-IR）、热重分析（TGA）以及N₂吸附-脱附曲线等表征证实了其结构、热稳定性以及多孔性.随后在聚苯胺（PANI）修饰的多孔氧化铝基底表面原位生长了一层致密连续的DMTA-COF膜.通过XRD和扫描电子显微镜（SEM）的表征证实了DMTA-COF膜具有较高的结晶性以及良好的共生性.由于极性的醚氧基团与电四极矩分子CO₂之间较强的相互作用进一步提高了希弗碱类型的DMTA-COF对CO₂的亲和力，从而增强了DMTA-COF膜的吸附扩散效应.在常温常压下，DMTA-COF膜的H₂/CO₂双组分分离系数为8.3，所对应的H₂渗透通量高达6.3×10^－7 mol·m^－2·s^－1·Pa^－1.
关键词: 共价有机骨架, 晶体结构, 膜, 气体分离, H₂纯化
Herein, we employ 2,5-dimethoxyterephthalaldehyde (DMTA) containing ether oxygen group in the structure as the construction unit to react with tetra-(4-anilyl)-methane (TAM) through Schiff-based condensation reaction in a Teflon-lined autoclave to synthesize a novel three-dimensional covalent organic framework named DMTA-COF. Furthermore, the condensation reaction was confirmed by Fourier transform infrared spectroscopy (FT-IR). The crystal structure of DMTA-COF was analyzed by the powder X-ray diffraction (PXRD) measurement in conjunction with structural simulation. The morphology, thermal stability, porosity and pore distribution of DMTA-COF were measured by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N₂ adsorption-desorption at 77 K. The high affinity for CO₂ adsorption was also confirmed by low pressure CO₂ sorption. Considering the relatively small pore size and the strong CO₂ adsorption interaction of DMTA-COF due to an abundant of ether oxygen group and imine linkage, we synthesized one continuous supported DMTA-COF membrane for H₂/CO₂ separation. In our study, the porous Al₂O₃ support surface was first coated with polyaniline (PANI) and was then further functionalized with aldehyde groups by reaction with DMTA at 150 ℃ for 1 h. Finally, in situ growth of the COF membrane utilizing the covalent linkage yielded a novel continuous DMTA-COF membrane. X-ray diffraction (XRD) result indicated that the DMTA-COF membrane was pure phase and had high crystallinity. From SEM characterization, we could see that the DMTA-COF membrane was compact and well intergrowth and adhered to the support tightly. Gas separation performance results shown that DMTA-COF membrane had a high H₂ permeance and selectivity of H₂/CO₂. For DMTA-COF membrane, the 1∶1 binary mixture gas separation factors of H₂/CO₂ calculated as the gas molar ratios in permeate and retentate side was 8.3 at room temperature and atmospheric pressure. And H₂/CO₂ separation factor of DMTA-COF membrane exceeded the corresponding Knudsen coefficient (4.7), with H₂ permeance of up to 6.3×10^－7 mol·m^－2·s^－1·Pa^－1. Because of its outstanding characteristics, the novel DMTA-COF membrane is expected to be widely used in the field of H₂ purification and separation.
Key words: covalent organic framework, crystal structure, membranes, gas separation, H₂ purification


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