Graphene oxide (GO) membranes have shown great potential for water purification, but their permeability and antipressure ability are poor, which limits their practical applications. In this study, two‐dimensional graphitic carbon nitride (g‐C3N4) nanosheet‐intercalated GO (GOCN) membranes were developed to improve the separation performance of GO membranes, especially under high operating pressure. After incorporation of the g‐C3N4 nanosheets, the amount of permeable nanochannels (wrinkles or corrugation) in the membrane increased; hence, the water permeance was effectively improved (twice as high as that of GO membranes). Moreover, the antipressure performance of the GOCN membranes was significantly enhanced (even below 0.5 MPa pressure) as the nanochannels in the composite membranes become stable and rigid due to the support of the pressure‐resistant g‐C3N4 nanosheets. The good separation performance demonstrates that the intercalation of g‐C3N4 is an effective strategy to improve the GO‐based membrane properties, which can promote their application in water purification.

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Covalent organic frameworks (COFs) are a disruptive material platform for various novel applications including nanofiltration for water purification due to their excellent physicochemical features. Nevertheless, the currently available approaches for preparing COF membranes need stringent synthesis conditions, prolonged fabrication time, and tedious post‐processing, leading to poor productivity. Herein, a simple and efficient layer‐by‐layer stacking assembly strategy is developed based on electrophoretic deposition (EPD) to rapidly generate ionic COF membranes due to the uniform driving force for nanosheet assembly. A new two‐cell EPD design avoids the usual EPD problems such as bubbles and acidic/alkaline microenvironments in the near‐electrode region in aqueous EPD processes. Ultrathin COF membranes with homogenous structures can be produced within several minutes. Consequently, the prepared COF membranes exhibit outstanding permselectivity and possess good stability and anti‐pressure ability due to their uniform architecture and unique chemical composition.

Two-dimensional graphitic carbon nitride (g-C3N4) nanosheets are ideal candidates for membranes because of their intrinsic in-plane nanopores. However, non-selective defects formed by traditional top-down preparation and the unfavorable re-stacking hinder the application of these nanosheets in gas separation. Herein, we report lamellar g-C3N4 nanosheets as gas separation membranes with a disordered layer-stacking structure based on high quality g-C3N4 nanosheets through bottom-up synthesis. Thanks to fast and highly selective transport through the high-density sieving channels and the interlayer paths, the membranes, superior to state-of-the-art ones, exhibit high H2 permeance of 1.3 × 10−6 mol m−2 s−1 Pa−1 with excellent selectivity for multiple gas mixtures. Notably, these membranes show excellent stability under harsh practice-relevant environments, such as temperature swings, wet atmosphere and long-term operation of more than 200 days. Therefore, such lamellar membranes with high quality g-C3N4 nanosheets hold great promise for gas separation applications.

Mixed protonic–electronic conducting (MPEC) ceramic membranes with high H2 permeability and stability are significant for practical H2 separation. CO2‐tolerant lanthanum tungstate oxides have received much attention, but their low H2 permeability is their main problem for membrane applications. Herein, an efficient in‐situ exsolution strategy is proposed to enhance the H2 permeability and CO2 stability of lanthanum tungstate‐type membranes. During H2 permeation, the catalytic Pd nanoparticles are in‐situ generated from the bulk oxide lattices and dispersed evenly on the membrane surfaces, which greatly promotes the H2 surface exchange kinetics. Also, the protonic conductivity of the membranes is effectively improved through the introduction of Pd. Consequently, the H2 permeation flux is increased by 3.5 times and a maximum H2 flux of 1.3 mL min−1 cm−2 is achieved at 1000 °C through the La5.5(W0.6Mo0.4)0.95Pd0.05O11.25‐δ (LWMPd) membrane. The LWMPd membrane shows outstanding long‐term chemical stability during 300 h continuous operation in a CO2‐containing atmosphere. Therefore, this in‐situ exsolution formation of Pd nanoparticles provides effective guidance for developing competitive MPEC membranes for H2 separation and purification.