Preparation of Covalent Organic Framework/PDMS Mixed Matrix Membranes for Efficient Ethanol Recovery via Pervaporation

Bioethanol, as a renewable energy source, is receiving continuous attention for efficient recovery in aqueous solution. In this work, high-permeable ethanol mix matrix membranes (MMMs) were prepared by incorporating covalent organic framework-300 (COF-300) into polydimethylsiloxane (PDMS) by solution blending. The morphology, functional groups, surface roughness, contact angle, and swelling degree of MMMs before and after COF-300 loading were characterized and analyzed. The encouraging finding is that the incorporation of porous COF-300 particles results in a significant enhancement of the hydrophobicity and ethanol affinity, which in turn increases the total flux and separation factor. The pervaporation results showed that the total flux reached 1515.28 g·m^-2·h^-1 and the separation factor reached 8.7 at a 3 wt % COF loading. Compared with pure PDMS, the total flux and separation factor of MMMs increased by 71.4 and 7.8%, respectively. Primarily based on the unique pore structure characteristics of COF-300, it can provide ultrafast channels for ethanol molecules. At the same time, COF-300 itself is a porous hydrophobicity particle with good ethanol affinity, which will promote the diffusion of ethanol molecules, further promote membrane swelling, and thus increase the separation factor and flux. Moreover, the MMMs in this work exhibited satisfactory stability during 6 months of continuous operation. Therefore, COF-300 is expected to be an ideal filler material to improve the separation performance of permeable ethanol membranes.