Research on two-dimensional materials in the past decades has brought many insights of low-dimensional science on a wide range of related topics. As a novel two-dimensional structure, the atomic-scale capillaries which can conceptually be seen as the empty space left by removing few layers of two-dimensional materials from their bulk van der Waals crystals offer a unique platform of investigating physical and chemical processes of ions, molecules, and atoms under two-dimensional confinements. Investigation of many important problems, such as capillary condensation and water network structure that are difficult to be explored experimentally in other confinement structures, has now been accessible; two-dimensional migration of ions, water, and gases shows abnormal transport properties beyond conventional theory prediction; influence of quantum effect to molecule permeation is observable even at room temperature. All these discoveries greatly extend our fundamental understandings of nano-science, and stimulate the development of potential applications. We review the fabrication of these two-dimensional capillaries which are created by the assembly of van der Waals heterostructures, and discuss the ultimate steric effects in the smallest possible confinements. Exotic interactions between capillary interior and confined particles are also summarized. When coupled with external stimuli, these channels exhibit tunable mass transport behaviors, which not only gives feedback to the mechanism understanding but in turn guides the channel structure optimization.

When ''cut off'' continuous and uniform basal plane of two-dimensional (2D) materials, edges appear at cross-sections. Such edges with unique one-dimensional (1D) structures and bound-states significantly alter materials’ local chemical activities and have been extensively investigated as model platforms for investigating structure–property–performance relationships for chemistry. Many interesting phenomena have been discovered in the past decades, highlighting the importance of interactions between active species and edge atoms at the atomic level and making 1D edges as emerging catalysts with high efficiency, promising candidates for battery and electrochemical contacts. Here, this review focuses on the recent progress of edge synthesis and structural engineering methods, understanding of edge structure–activity mechanisms, and potential applications using edge sites. Challenges and prospects are also envisioned.

Solar-driven water evaporation is a sustainable method to purify seawater. Nevertheless, traditional volumetric water-evaporation systems suffer from the poor sunlight absorption and inefficient light-to-thermal conversion. Also, their anti-bacterial and anti-fouling performances are crucial for the practical application. Herein, we introduce reduced graphene oxide (RGO) with broadband absorbance across the entire solar spectrum, and polypyrrole (PPy), an antibacterial polymer with efficient solar absorption and low thermal conductivity, to develop integrated RGO/PPy aerogel as both the solar absorber and evaporator for highly efficient solar-driven steam generation. As a result, the RGO/PPy aerogel shows strong absorption and good photothermal performance, leading to an evaporation rate of 1.44 kg·m⁻²·h⁻¹ and high salt rejection (up to 99.99%) for real seawater, with photothermal conversion efficiency > 90% under one sun irradiation. The result is attributed to the localized heat at the air–water interface by the RGO/PPy and its porous nature with functional groups that facilitates the water evaporation. Moreover, the RGO/PPy demonstrates excellent durability and antibacterial efficiency close to 100% for 12 h, crucial characteristics for long-term application. Our well-designed RGO/PPy aerogel with efficient water desalination performance and antibacterial property provides a straightforward approach to improve the solar-driven evaporation performance by multifunctional materials integration, and offers a viable route towards practical seawater desalination.