Separating 2-phenylethanol from aqueous solution by mixed matrix composite membranes based on beta-cyclodextrin metal organic frameworks

Natural 2-phenylethanol (2-PE) is a spice with the rose-like fragrance and non-toxicity to human, whose classical separation technique from the plants has faced great challenge owing to high energy consumption, chemical engineering safety and environmental pollution issue. Herein, the mixed matrix composite membranes (MMCMs) for 2-PE pervaporation separation from aqueous solution were engineered by incorporating beta-cyclodextrin metal organic frameworks (β-CD-MOFs) with a large amount of hydroxyl groups and hydrophobic cavities into the polydimethylsiloxane (PDMS) matrix. The as-prepared MMCMs exhibited excellent 2-PE pervaporation separation performance with the permeation total flux, separation factor, and pervaporation separation index of 1186 g m−2 h−1, 21.3 and 24076 g m−2 h−1, respectively, which increased by 25.8 %, 129.0 % and 208.6 % compared with that of the pristine one, outperforming MMCMs embedding with other fillers, when 2-PE concentration in aqueous solution is 6000 ppm. This can be explained by the fact that the hydrogen bonding and hydrophobic interactions between β-CD-MOFs and 2-PE improves 2-PE dissolution in the membrane, thus enhancing the 2-PE solubility selectivity in MMCMs. Thus, MMCMs had specific recognition for 2-PE over a spice maltol, whose 2-PE flux and the 2-PE/water separation factor only reduced by 15.0 % and 37.6 % respectively, when maltol concentration increased to 2000 ppm in 6000 ppm of 2-PE aqueous solution. Besides, resultant MMCMs showed long-term stability for over 140 h with the average permeation total flux of 1317 g m−2 h−1 and the separation factor of 21.8.