Metal–organic frameworks (MOFs) are increasingly utilized for the design of molecular sieve membranes with unprecedented separation performance, mainly attributed to their nanopore structure and superior polymer affinity. Herein, UiO-66-NH₂ crystals were synthesized as functional nanofillers to prepare polyamide (PA) composite membranes. The aqueous solution containing piperazine and evenly dispersed UiO-66-NH₂ was transferred onto a membrane surface via vacuum filtration, followed by interfacial polymerization (IP) with trimesoyl chloride (TMC). Covalent bonding between the terminal amine groups of Zr-MOFs and TMC enables the stable immobilization of MOF crystals in the formed PA layer. The positioned MOF nanoaggregates that serve as robust nodes connected by the formed continuous striped film after IP reaction facilitate a rough, fishnet-like surface, which has a larger surface area in comparison to the nodular structure. This unique structure is beneficial for the creation of increased water transport channels, while not compromising the salt rejection. The best performing TFN membranes with a loading mass of 20.5 μg cm⁻² exhibited a favorable Na₂SO₄ rejection of 97.5%, and excellent water permeability (30.8 L m⁻² h⁻¹ bar⁻¹). This facile, controlled loading of hydrophilic MOFs via vacuum filtration allows fabrication of crumpled PA membranes with outstanding separation performance.

Kevlar aramid nanofibers (KANFs) are a fascinating class of one-dimensional organic nanomaterials with high-performance and show high potential in preparation of membranes for separation and energy conversion.

Surfaces with superhydrophobicity and underwater superoleophobicity have attracted tremendous attention in oil/water separation due to their high separation efficiency. The key challenge lies in the construction of a hierarchically micro/nanoscale structural surface. In this study, a hierarchically micro/nanoscale structural surface was synthesized by a simple two-step designing of a unique three-dimensional multiscale ZIF-L on a 3D printed membrane for a superhydrophobic and underwater superoleophobic surface. This approach involves the synthesis of two novel ZIF-Ls. The first ZIF-L synthesized by using an aqueous system with a relatively high concentration of 2-methylimidazole (Hmim) and zinc ions displayed a three-dimensional leaf-crossed structure. The second micro/nanostructural ZIF-L is obtained by a second growth of small flat rod-shape and needle-like ZIF-Ls on the surface of leaf-crossed ZIF-L. Two-step deposition of such multiscale ZIF-Ls on a rough 3D printed PA membrane yields a perfect multiscale micro/nano-structural membrane. This hierarchical surface endows the membrane with superwetting properties. When being coated with PDMS, this membrane exhibits extreme superhydrophobicity with a sliding water contact angle as low as 1.56° and superoleophilicity with an oil contact angle of zero simultaneously. In addition, after being wetted with water, it demonstrates superhydrophilicity and underwater superoleophobicity. When these membranes are applied for oil/water separation, a high oil rejection of over 99% and an oil flux of over 24 000 L (m⁻² h⁻¹) are attained. The stepwise ZIF-L design provides a facile and effective strategy to construct multiscale micro/nano-structures.

Membranes with unparalleled solvent permeance and excellent selectivity are needed to reduce the energy input by molecular separations in organic liquids. A novel organic solvent nanofiltration (OSN) membrane with high flux was prepared from aramid nanofibers (ANFs) with in situ incorporation of microspheres. The ANF was dissociated from Kevlar aramid fibers in dimethyl sulfoxide (DMSO)/potassium hydroxide (KOH) solution and interacted with polyethyleneimine (PEI) through non-covalent interactions, forming ANF/PEI microparticles. The ANF/PEI OSN membrane was successfully fabricated by non-solvent induced phase separation and post-treatment. Dead-end filtration experiments showed that the permeance of the ANF/PEI membrane increased by a factor of over four (6.0 ± 0.5 L m⁻² h⁻¹ bar⁻¹vs. 1.4 ± 0.1 m⁻² h⁻¹ bar⁻¹). Meanwhile, the unique polymeric layered nano/micro structure of the ANF/PEI thin film membrane contributed to the ultrafast organic solvent permeance for tetrahydrofuran (THF) (20.5 m⁻² h⁻¹ bar⁻¹) and acetone (11.2 m⁻² h⁻¹ bar⁻¹). Finally, the ANF/PEI membrane significantly promotes ethanol permeance, without compromising its high selectivity when it is treated with methanol. The highest permeability was 9.1 L m⁻² h⁻¹ bar⁻¹ with an RB rejection of 98.4% after 6 d of methanol treatment. The ANF/PEI OSN membrane showed a good stability in a long-term experiment. This facile construction of nanofiber membranes with in situ modification provides a new direction for high performance OSN membranes.