Designing Janus Two-Dimensional Porous Materials for Unidirectional Transport: Principles, Applications, and Challenges

Unidirectional liquid transport, facilitated by asymmetric properties or structures, has gained prominence in applications, such as liquid manipulation, water harvesting, and microfluidic systems. Janus two-dimensional (2D) porous materials, known for their unique capacity for unidirectional liquid transport, have attracted significant interest. This phenomenon is driven by the capillary force and Laplace pressure, enabling efficient liquid flow in a preferred manner. Leveraging this process, Janus 2D porous materials have found applications in a series of multiphase processes without additional energy input. Despite a growing body of researches in this area, there is a notable absence of a comprehensive review focusing on the fundamentals of Janus 2D porous materials with unidirectional liquid transport capacity. This Review aims to address this gap by summarizing present hypotheses, factors influencing unidirectional transport, construction strategies, and potential applications. Furthermore, the future of this field is forecast to present challenges and opportunities.