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.