A Bioinspired Capillary Force‐Induced Driving Strategy for Constructing Ultra‐Low‐Pressure Separation Membranes

Abstract The development of low‐pressure or pressureless self‐driven membranes is important for saving energy and overcoming the critical trade‐off effect in membrane separation processes. However, conventional self‐driven membranes rely on gravity, which is effective in the separation of large‐sized materials but is still ineffective in the fine separation of small molecules. Herein, inspired by the capillary effect that exists in nature, a capillary force‐induced membrane‐driving strategy for fine separation at ultra‐low pressures is demonstrated. Hydrophilic nanoparticles are prepared by a cross‐linking reaction between tannic acid and 3‐aminopropyltriethoxysilane and then introduce them into membrane pores to simulate sand accumulation with an aim to generate the capillary force. The membrane is then used in ultra‐low pressure membrane separation. Interestingly, it is found that the membrane has excellent performance in the separation of dye/salt mixtures (dye rejection > 99%, salt rejection < 10%) and a high permeate flux (160 L m⁻² h⁻¹) under near “zero pressure” conditions. Moreover, the structural stability of the membrane is verified. Introducing capillary forces into membranes as an autonomous driving force can be a promising universal approach that can be added up to the toolbox for the efficient preparation of separation membranes.