Fluorinated β-CD-MOF strengthened 2-phenylethanol pervaporation separation of mixed matrix membranes

Abstract

Beta-cyclodextrin metal-organic framework (β-CD-MOF) is porous crystalline material formed by coordinating β-cyclodextrin with potassium ion, which can significantly enhance the pervaporation separation performance of mixed matrix membranes (MMMs). However, achieving MMMs with high 2-phenylethanol (2-PE) pervaporation separation performance poses challenges due to the lack of affinity sites. Herein, β-CD-MOF was modified with 3-glycidoxypropyltrimethoxysilane (KH560) to prepare KH560-functionized β-CD-MOF (K-βMOF). Subsequently, fluorinated β-CD-MOF (F–K-βMOF) was prepared via a ring-opening reaction between the epoxy groups of K-βMOF and amine groups of 1,4-bis(4-amino-2-trifluoromethylphenoxy) benzene. Then, MMMs were fabricated by incorporating F–K-βMOF into a PDMS matrix, which exhibited excellent 2-PE pervaporation separation performance, achieving a total flux of 1226 g m⁻² h⁻¹, a separation factor of 31.83, and a pervaporation separation index of 37807 g m⁻² h⁻¹. These values were 1.48, 2.67, and 4.23 times higher than those of the pure PDMS membrane, and 1.29, 1.74, and 2.23 times higher than those of MMMs containing β-CD-MOF, respectively. This is because –CF₃ groups and benzene ring in F–K-βMOF enhance the affinity for 2-PE through hydrogen bonding, hydrophilic-hydrophobic and π-π interactions. When the concentration of maltol in the 2-PE aqueous solution increased to 1200 ppm, the flux and separation factor of 2-PE decreased by 39 % and 37 %, respectively. The separation factor of 2-PE decreased from 31 to 20, which was still higher than that of maltol, indicating that MMMs exhibited efficient molecular recognition capability. Furthermore, MMMs exhibited exceptional durability during 168 h testing, highlighting a great potential for 2-PE separation in industrial application.