Since the discovery of 2D materials, 2D material nanofiltration (NF) membranes have attracted great attention and are being developed with a tremendously fast pace, due to their energy efficiency and cost effectiveness for water purification. The most attractive aspect for 2D material NF membranes is that, anomalous water and ion permeation phenomena have been constantly observed because of the presence of the severely confined nanocapillaries (<2 nm) in the membrane, leading to its great potential in achieving superior overall performance, e.g., high water flux, high rejection rates of ions, and high resistance to swelling. Hence, fundamental understandings of such water and ion transport behaviors are of great significance for the continuous development of 2D material NF membranes. In this work, the microscopic understandings developed up to date on 2D material NF membranes regarding the abnormal transport phenomena are reviewed, including ultrafast water and ion permeation rates with the magnitude several orders higher than that predicted by conventional diffusion behavior, ion dehydration, ionic Coulomb blockade, ion–ion correlations, etc. The state‐of‐the‐art structural designs for 2D material NF membranes are also reviewed. Discussion and future perspectives are provided highlighting the rational design of 2D material membrane structures in the future.

Lithium metal batteries (LMBs) show tremendous potential in energy storage due to ultrahigh energy densities. Nevertheless, maintaining a stable solid electrolyte interphase (SEI) and suppressing the growth of dendrites are hard to achieve with conventional liquid electrolytes. Gel/solid polymer electrolytes are sought-after candidates to block dendrite growth, while they still suffer from poor ionic conductivity and an incompatible interphase. Herein, a borate-rich gel polymer electrolyte with a 3D cross-linked structure (3D-BGPE) is designed to settle these problems. By incorporating anion-trapping boron moieties into a 3D configuration via an in situ strategy, the 3D-BGPE presents high ionic conductivity (8.4 × 10⁻⁴ S cm⁻¹), near single ion conduction (Li⁺ transference number of 0.76) and constructs a stable and conductive SEI layer on the lithium anode. Accordingly, the LMBs employing the 3D-BGPE can effectively inhibit the dendrite growth and maintain 89.73% capacity retention after 400 cycles. A promising approach to design highly effective electrolytes for safe and long-life LMBs is provided in this work.