Liquid-infused aerogel membranes with reverse functions enable on-demand emulsification and demulsification

The introduction of a functional liquid into a porous membrane has appeared recently. Yet, how to selectively confine the functional liquid into a hierarchically porous matrix to achieve reverse functions of emulsification and demulsification in one membrane remains elusive. Here the hierarchical porous aerogel membrane can be created by simultaneously taking advantage of reprotonation, non-solvent-induced phase separation and chemical-triggered sol–gel transition of the mixture of aramid nanofibre and polyvinylpyrrolidone to only confine the aqueous phase in nano spaces. By regulating the given pressure, selectively in situ liquid-infused aerogel membranes (SILAMs) can be commanded for emulsification or demulsification. In emulsification mode, SILAMs can produce uniform emulsions with tailorable sizes and outstanding stability for up to 10 weeks. Compared with other emulsification membranes, SILAMs produce smaller-sized emulsions at lower energy consumption. Notably, the discrimination among micro- and nano-emulsions is showcased by rationalizing the pore structure of the hierarchical porous aerogel membrane and tuning the driven pressure on SILAM. In a demulsification manner, SILAMs can realize efficient oil and water separation with sustained anti-fouling performance from both emulsions and mixture with arbitrary oil/water ratio. The oil–water separation factor of SILAMs is up to 99.97% and can be cycled up to 30 times to purify real ship wastewater. These unique SILAMs can promote the development of smart membranes for various applications, ranging from water treatment, materials fabrication and food industry to the petrochemical industry. Liquid-infused porous membranes with rich interfacial properties have been developed and demonstrate potential across diverse applications. The in situ infusion of selected liquids into aerogel membranes enables on-demand emulsification and demulsification, conserving energy and exhibiting anti-fouling characteristics.