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Metal/covalent-organic framework (MOF/COF) membranes have attracted increasing research interest and have been considered as state-of-the-art platforms applied in various environment- and energy-related separation/transportation processes. To break the trade-off between permeability and selectivity to achieve ultimate separation, recent studies have been oriented towards how to design and exploit ultrathin MOF/COF membranes (i.e. sub-1 μm-thick). Given great advances made in the past five years, it is valuable to timely and systematically summarize the recent development and shed light on the future trend in this multidisciplinary field. In this review, we first present the advanced strategies in fabricating ultrathin defect-free MOF/COF membranes such as in situ growth, contra-diffusion method, layer-by-layer (LBL) assembly, metal-based precursor as the pre-functionalized layer, interface-assisted strategy, and laminated assembly of MOF/COF nanosheets. Then, the recent progress in some emerging applications of ultrathin MOF/COF membranes beyond gas separation is highlighted, including water treatment and seawater desalination, organic solvent nanofiltration, and energy-related separation/transportation (i.e. lithium ion separation and proton conductivity). Finally, some unsolved scientific and technical challenges associated with future perspectives in this field are discussed, inspiring the development of next-generation separation membranes.

Surface modification has been well recognized as a promising strategy to design and exploit diversified functional materials. However, conventional modification strategies usually suffer from complicated manufacture procedures and lack of universality. Herein, a facile, robust, and versatile approach is proposed to achieve the surface functionalization using dopamine and acrylate monomers via a one-step polymerization and codeposition process. The gel permeation chromatography, proton nuclear magnetic resonance, liquid chromatography-mass spectrometry, and UV-visible spectra results indicate that dopamine possesses the capability of triggering the polymerization of acrylate monomers into high-molecular-weight products, and the inherent adhesive ability of polydopamine can assist the polymerized products to deposit on various substrates. Besides, protein-resistant, antibacterial, and cell adhesion-resistant surfaces can be easily fabricated via the finely designed integration of corresponding acrylate monomers into the codeposition systems. This approach of in situ polymerization and codeposition significantly simplifies the fabrication process and provides more manifold choices for surface modification, which will open a new door for broadening the applications of polydopamine-based coatings.

Nanofiltration membranes (NFMs) with a high water permeation flux and salt rejection are extremely desirable due to their low energy consumption and superior separation efficiency in practical appl...

Mussel-inspired polydopamine (PDA) coatings have been broadly exploited for constructing functional membrane surfaces. One-step codeposition of PDA with antifouling polymers, especially zwitterionic polymers, has been regarded as a promising strategy for fabricating antifouling membrane surfaces. However, one challenge is that the codeposition is usually a slow process over 10 h or even several days. Herein, we report that CuSO4/H2O2 is able to notably accelerate the codeposition process of PDA with poly(sulfobetaine methacrylate) (PSBMA). In our case, PSBMA is facilely anchored to the polypropylene microporous membrane (PPMM) surfaces within 1 h with the assistance of PDA because of its strong interfacial adhesion. The PDA/PSBMA-coated PPMMs show excellent surface hydrophilicity, high water permeation flux (7506 ± 528 L/m2·h at 0.1 MPa), and an outstanding antifouling property. Moreover, the antifouling property is maintained after the membranes are treated with acid and alkali solutions as well as organ...

Structural colors are in increasing demand in many fields such as color displays, sensor devices, and anti-counterfeiting labels. Herein, large-scale and angle-independent structural colors were constructed from polydopamine (PDA) coatings with a high refractive index and uniformity. This strategy can be utilized to facilely fabricate various color patterns. These structural colors also display high solvent resistance and excellent universality to a series of substrates. Moreover, stimuli-responsive structural colors can be easily synthesized via the co-deposition of PDA with poly(N-isopropylacryl-amide). To the best of our knowledge, this is the first time that structural colors from PDA-based coatings have been reported.

Transition metal dichalcogenide (TMD) nanosheets have evoked enormous research enthusiasm and have shown increased potentials in the biomedical field. However, a great challenge lies in high-throughput, large-scale, and eco-friendly preparation of TMD nanosheet dispersions with high quality. Herein, we report a universal polyphenol-assisted strategy to facilely exfoliate various TMDs into monolayer or few-layer nanosheets. By optimizing the exfoliation condition of molybdenum disulfide (MoS

Zwitterionic polymers are continually suggested as promising alternatives to tune the surface/interface properties of materials in many fields because of their unique molecular structures. Tremendous efforts have been devoted to immobilizing zwitterionic polymers (polyzwitterions, PZIs) on the material surfaces. However, these efforts usually suffer from cumbersome and time-consuming procedures. Herein we report a one-step strategy to facilely achieve the bioinspired polydopamine/polyzwitterion (PDA/PZI) coatings on various substrates. It requires only 30 min to form PDA/PZI coatings by mixing oxidant, dopamine, and zwitterionic monomers, including carboxybetaine methacrylate (CBMA), sulfobetaine methacrylate (SBMA), and 2-methacryloxyethyl phosphorylcholine (MPC). These bioinspired coatings display multifunctional properties such as underwater antioil-adhesion and antifreezing thanks to their high hydrophilicity and underwater superoleophobicity. The coatings even show the antiadhesion property for crude oil with high viscosity. Therefore, the PDA/PZI-coated meshes are efficient for separating both light oil and crude oil from oil/water mixtures. All these results demonstrate that the one-step strategy is a facile approach to design and exploit the bioinspired PDA/PZI coatings for diverse applications.

A method of establishing a kinematic model for simulated railroad freight car impact based on the Runge-Kutta method is introduced in this paper. The model is solved based on numerical analysis to obtain the relationship of variables, furthermore providing a basis for determining the loading support and loading securement method.

Two-dimensional (2D) nanosheets have attracted extensive attention and have been considered as compelling nanofillers of polyamide-based nanofiltration membranes (NFMs) with thin film nanocomposite (TFN) frame. However, there still remains a big challenge, the poor compatibility between these 2D nanofillers and the polyamide matrix, significantly restricting their practical applications. Herein, we present TFN NFMs by incorporating tannic acid (TA) functionalized molybdenum disulfide (MoS2) nanosheets into the polyamide skin layers via typical interfacial polymerization of piperazine (PIP) and trimesoyl chloride (TMC). TA was employed to assist the aqueous exfoliation of bulk MoS2 into 2D nanosheets, and simultaneously served as the functional molecule to modify and stabilize the as-exfoliated MoS2 nanosheets in aqueous solutions. Thanks to the contribution of TA, the MoS2 nanosheets can be covalently linked into the skin layers through the reaction of TA and TMC, thus exhibiting excellent compatibility with polyamide matrix. Besides, the as-prepared TFN NFMs show promoted water permeation as high as 17.0 L/m2⋅h⋅bar without compromising the salt rejection of divalent ions (98.5%). Moreover, these high-performance TFN NFMs also possess outstanding long-term stability, with great implication for the practical applications.

Mussel-inspired polydopamine (PDA) coatings have been broadly exploited for constructing functional membrane surfaces. One-step codeposition of PDA with antifouling polymers, especially zwitterionic polymers, has been regarded as a promising strategy for fabricating antifouling membrane surfaces. However, one challenge is that the codeposition is usually a slow process over 10 h or even several days. Herein, we report that CuSO