ZIFs椭圆形孔窗的精细调控及糠醛/5-羟甲基糠醛吸附分离性能研究

在生物质催化炼制呋喃化合物的过程中，通常得到的是低浓度糠醛（Fur）和5-羟甲基糠醛（5-HMF）的混合物。基于Fur和5-HMF都是椭圆形分子，因此通过设计构筑和调控椭圆形孔窗的吸附剂可以实现Fur和5-HMF的筛分分离。选用二价钴盐和三种烷基取代基团逐渐增大的咪唑配体（2-乙基咪唑/2-eIm、2-丙基咪唑/2-pIm和2-丁基咪唑/2-bIm）合成了三种椭圆形孔窗尺寸逐渐减小的ANA拓扑ZIFs材料：ANA-[Co(eIm)₂]、ANA-[Co(pIm)₂]和ANA-[Co(bIm)₂]。首先解析了这三种ZIFs材料的晶体结构，并对其进行了PXRD、水蒸气吸附、N₂吸脱附和SEM等基本表征，然后采用静态吸附和动态柱吸附研究了这三种材料对Fur和5-HMF的吸附分离性能。静态吸附、单组分动态柱吸附以及综合速率模型模拟计算结果显示：ANA-[Co(pIm)₂]狭窄的椭圆形孔窗与Fur分子尺寸接近，但小于5-HMF，使得Fur分子可以吸附进入椭圆形孔窗，而5-HMF分子几乎不能通过。进一步在双组分Fur/5-HMF（5%/5%，质量分数）动态柱吸附中，ANA-[Co(pIm)₂]对Fur的吸附量为91.7 mg·g^-1，不吸附5-HMF。因此，通过改变咪唑配体取代基团精细调控ZIFs椭圆形孔窗尺寸，并利用ZIFs椭圆形孔窗的位阻效应实现了Fur和5-HMF的筛分分离。

Fine adjustment of elliptical windows of ZIFs and performances of adsorptive separation of furfural/5-hydroxymethylfurfural

In the process of refining furan compounds through biomass catalysis, a mixture of low concentration furfural (Fur) and 5-hydroxymethylfurfural (5-HMF) aqueous solution is usually obtained. Based on the fact that both Fur and 5-HMF are elliptical molecules, the sieving separation of Fur and 5-HMF can be achieved by designing and adjusting the elliptical windows of the adsorbents. In this paper, we used divalent cobalt salts and three imidazole ligands with gradually increasing alkyl substituent groups (2-ethylimidazole/2-eIm, 2-propylimidazole/2-pIm and 2-butylimidazole/2-bIm) to synthesize three ANA topology ZIFs materials with gradually decreasing elliptical windows: ANA-[Co(eIm)₂], ANA-[Co(pIm)₂] and ANA-[Co(bIm)₂]. Firstly, the crystal structures of these three ZIFs were analyzed, and basic characterizations such as PXRD, water vapor adsorption, N₂ adsorption and desorption, and SEM were performed, and then batch adsorption and dynamic column adsorption were used to study the adsorptive separation performance of the three materials for Fur and 5-HMF. The results of batch adsorption, single-component dynamic column adsorption and general rate model simulation calculations show that: narrow and elliptical window of ANA-[Co(pIm)₂] is close to the Fur molecular size, but smaller than 5-HMF, so that Fur molecular can be adsorbed into the elliptical windows, while 5-HMF molecular is hardly adsorbed and cannot pass through. Furthermore, the adsorption capacity of ANA-[Co(pIm)₂] for Fur in the binary-component Fur/5-HMF (5%/5%,mass ratio) dynamic column adsorption is 91.7 mg·g^-1, and 5-HMF is not adsorbed. Therefore, by changing the imidazole ligand substituent groups, the size of the elliptical windows of ZIFs was finely adjusted, and the steric hindrance effect of the elliptical windows of ZIFs was used to achieve the sieve separation of Fur and 5-HMF.