Advanced Development of Molecularly Imprinted Membranes for Selective Separation

Abstract

Molecularly imprinted membranes (MIMs), the incorporation of a given target molecule into a membrane, are generally used for separating and purifying the effective constituents of various natural products. They have been in use since 1990. The application of MIMs has been studied in many fields, including separation, medicine analysis, solid-phase extraction, and so on, and selective separation is still an active area of research. In MIM separation, two important membrane performances, flux and permselectivities, show a trade-off relationship. The enhancement not only of permselectivity, but also of flux poses a challenging task for membranologists. The present review first describes the recent development of MIMs, as well as various preparation methods, showing the features and applications of MIMs prepared with these different methods. Next, the review focuses on the relationship between flux and permselectivities, providing a detailed analysis of the selective transport mechanisms. According to the majority of the studies in the field, the paramount factors for resolving the trade-off relationship between the permselectivity and the flux in MIMs are the presence of effective high-density recognition sites and a high degree of matching between these sites and the imprinted cavity. Beyond the recognition sites, the membrane structure and pore-size distribution in the final imprinted membrane collectively determine the selective transport mechanism of MIM. Furthermore, it also pointed out that the important parameters of regeneration and antifouling performance have an essential role in MIMs for practical applications. This review subsequently highlights the emerging forms of MIM, including molecularly imprinted nanofiber membranes, new phase-inversion MIMs, and metal–organic-framework-material-based MIMs, as well as the construction of high-density recognition sites for further enhancing the permselectivity/flux. Finally, a discussion of the future of MIMs regarding breakthroughs in solving the flux–permselectivity trade-off is offered. It is believed that there will be greater advancements regarding selective separation using MIMs in the future.

Preparation of imidazole-modified paper membrane for selective extraction of gallic acid and its structural and functional analogues from Pomegranate Peel

“… 4–6 Membrane technology, 7 due to its selective permeation or retention and diverse application forms, has been widely used in the processes of separation, concentration, or purification of natural products with various industrial and scientific purposes. 8,9 As for regulating membrane affinity, which is a research focus and challenge, concept and practice have gradually evolved from extracting compounds with specific structures (structure-oriented) to extracting a class of compounds with desired pharmaceutical functions (function-oriented). There are several methods that could be referenced: (1) extrathermodynamics-based research: the relationship between chromatographic retention and physicochemical parameters of tested compounds has been described by means of linear free energy relationships (LFERs) or other derivative methods, 10–12 for better summarizing an applicable range of tested adsorbents and predicting separation conditions for new targets.…”