Progress in molecular-recognition smart membranes

Abstract

Membrane technology is playing an increasingly important role in modern life and global sustainable development. Despite significant achievements in membrane science, single-function membranes whose trans-membrane permeation cannot respond to environmental stimuli remain the most widely used. This is in contrast to the properties of natural cell membranes, whose environmental-stimuli-responsive channels regulate trans-membrane permeability. Inspired by this natural prototype, membrane scientists have devoted great effort to developing smart gating membranes that respond to artificial stimuli, to expand the application of membrane technology. Smart gating membranes can be prepared by using chemical or physical methods to load smart materials, acting as valves, onto porous substrates. The smart materials allow the control or self-regulation of membrane surface characteristics and/or permeation properties, including hydraulic permeability and diffusional permeability. To meet a growing number of technology needs, a wide range of smart gating membranes have been designed and fabricated: thermo-responsive, pH-responsive, molecular-responsive, light-responsive, magnetic-responsive, ion-strength-responsive, redox-responsive, electro-responsive, and hygro-responsive. Molecular-recognition smart membranes, which are among the most exciting and attractive stimuli-responsive smart gating membranes, have superbly low energy consumption and high efficiency. They are able to respond to specific molecules, and have myriad applications in controlled release, chemical or biological separations, water treatment, and tissue engineering. This review briefly introduces the design and application of three types of molecular-recognition smart membranes with different recognition mechanisms: host-guest, coupling, and chelation. Recent progress in the emerging applications of molecular-recognition smart membranes is also highlighted. This review provides valuable information and guidance for rational design of novel molecular-recognition membranes and intensification of membrane processes.