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Fast permeation and effective solute-solute separation provide the opportunities for sustainable water treatment, but they are hindered by ineffective membranes. We present here the construction of a nanofiltration membrane with fast permeation, high rejection, and precise Cl-/SO42- separation by spatial and temporal control of interfacial polymerization via graphitic carbon nitride (g-C3N4). The g-C3N4 nanosheet binds preferentially with piperazine and tiles the water-hexane interface as revealed by molecular dynamics studies, thus lowering the diffusion rate of PIP by one order of magnitude and restricting its diffusion pathways towards the hexane phase. As a result, membranes with nanoscale ordered hollow structure are created. Transport mechanism across the structure is clarified using computational fluid dynamics simulation. Increased surface area, lower thickness, and a hollow ordered structure are identified as the key contributors to the water permeance of 105 L m2·h−1·bar−1 with a Na2SO4 rejection of 99.4% and a Cl-/SO42- selectivity of 130, which is superior to state-of-the-art NF membranes. Our approach for tuning the membrane microstructure enables the development of ultra-permeability and excellent selectivity for ion-ion separation, water purification, desalination, and organics removal.

Separation of propylene (C3H6) and propane (C3H8) is a vital step for the manufacture of high-purity C3H6 as an important energy source and critical raw material in the petrochemical industry. Due to their similar sizes and properties, the separation of C3H6 and C3H6 is challenging and currently relies on energy-intensive cryogenic distillation. Metal–organic framework (MOF)-assisted adsorptive separation and membrane-based separation are revolutionary energy-saving technologies that can enable efficient gas purification under mild conditions. This review presents the current progress in C3H6/C3H8 separation achieved with MOFs and MOF-based membranes. The different separation mechanisms (including equilibrium separation, kinetic separation, gate-opening effect, molecular sieving, and combination of them) along with the materials design principles that contribute to benchmark C3H6/C3H8 separation are discussed. Diverse creative strategies for the fabrication of high-quality MOF membranes (both continuous membranes and mixed-matrix membranes) to surpass the tradeoff between selectivity and gas permeability are summarized. Lastly, this review also outlines the major challenges and opportunities of MOFs to be used for practical C3H6/C3H8 separation.

Developing advanced porous materials with industrial potential to separate multicomponent gas mixtures that are structurally similar is a crucial but challenging task. Here, we report the efficient one-step separation of...

Surface pattern is a promising approach to enhance membrane performance while contradictory results have been reported on its impact on concentration polarization.Here, we provide an experimental and modeling study of the concentration polarization on patterned membranes by varying pattern size, solute size, surface hydrophilicity, and membrane orientation. Interesting trends were observed when comparing different membrane orientations, where relative concentration polarization degree (CPD) was found depend on molecular weight. Salts and small organic molecules encountered more severe CPD in the transverse mode, while molecules larger than a threshold value showed a different trend. Such threshold molecular weight increased at larger pattern size. Simulation results were consistent with experimental observations, and revealed the critical role of diffusivity on such phenomena. Results also showed more severe concentration polarization on patterned membranes in both parallel and transverse modes in most cases, compared to smooth membrane.