Graphene oxide (GO) membranes continue to attract intense interest due to their unique molecular sieving properties combined with fast permeation rates 1-9 . However, the membranes' use has been limited mostly to aqueous solutions because GO membranes appear to be impermeable to organic solvents 1 , a phenomenon not fully understood yet. Here, we report efficient and fast filtration of organic solutions through GO laminates containing smooth two-dimensional (

It is highly desirable to reduce the membrane thickness in order to maximize the throughput and break the trade-off limitation for membrane-based gas separation. Two-dimensional membranes composed of atomic-thick graphene or graphene oxide nanosheets have gas transport pathways that are at least three orders of magnitude higher than the membrane thickness, leading to reduced gas permeation flux and impaired separation throughput. Here we present nm-thick molecular sieving membranes composed of porous two-dimensional metal-organic nanosheets. These membranes possess pore openings parallel to gas concentration gradient allowing high gas permeation flux and high selectivity, which are proven by both experiment and molecular dynamics simulation. Furthermore, the gas transport pathways of these membranes exhibit a reversed thermo-switchable feature, which is attributed to the molecular flexibility of the building metal-organic nanosheets.

It is challenging to introduce pendent sulfonic acid groups into modularly built crystalline porous frameworks for intrinsic proton conduction. Herein, we report the mechanoassisted synthesis of two sulfonated covalent organic frameworks (COFs) possessing one-dimensional nanoporous channels decorated with pendent sulfonic acid groups. These COFs exhibit high intrinsic proton conductivity as high as 3.96 × 10(-2) S cm(-1) with long-term stability at ambient temperature and 97% relative humidity (RH). In addition, they were blended with nonconductive polyvinylidene fluoride (PVDF) affording a series of mixed-matrix membranes (MMMs) with proton conductivity up to 1.58 × 10(-2) S cm(-1) and low activation energy of 0.21 eV suggesting the Grotthuss mechanism for proton conduction. Our study has demonstrated the high intrinsic proton conductivity of COFs shedding lights on their wide applications in proton exchange membranes.

The modulated synthesis of metal−organic frameworks (MOFs) remains empirical and challenging. Modulators are often applied and assumed capable of facilitating crystal growth by adjusting the reaction kinetics. However, most of the current studies are based on qualitative analysis and performance-leading synthesis, while no quantitative insights between modulator feature and MOF performance have been offered. In this work, we carried out a comprehensive study of the effects of three modulators (acetic acid, formic acid, trifluoroacetic acid) on the water-based modulated synthesis of UiO-66-type MOFs by using Zr or Hf as the building block and fumarate as the ligand. The modulator effects on crystallinity, yield, morphology, pore size, defects, porosity, stability, and gas separation performance of resultant MOFs have been discussed. A relationship between optimal molar ratio y and pK a value of modulator x is modeled as y = 12.72 + 0.193 × exp(1.276x). For MOF synthesis using ligands of different acidity, it tends to follow the equations of y = −40.78 + 39.1x and y = −21.7 + 25.58x for acetic acid and formic acid, respectively. Our results have thus provided pioneering quantitative analysis and synthetic guidelines on the further synthesis of water-stable MOFs that require modulators.

We herein report a facile preparation of graphene oxide (GO) membranes including three steps: (1) mild freeze–thaw exfoliation to get large GO nanosheets, (2) purification of exfoliated GO nanosheets through pH adjustment, and (3) spin coating to fabricate smooth GO membranes with uniformly aligned GO nanosheets. The fabricated GO membranes are subject to single gas permeation tests, with the obtained gas permeance in the order He > H2 ≫ CH4 > CO2 > N2 ≫ SF6, indicating a dominant molecular sieving separation mechanism. The H2/CO2 mixed gas permeation tests reveal H2 permeance up to 3.4 × 10–7 mol/(m2·s·Pa) and a H2/CO2 separation factor up to 240, which are among the best of all the reported membranes for H2/CO2 separation. The separation factor drops to 47 at a higher temperature of 120 °C, but the H2 permeance is further increased to 6.7 × 10–7 mol/(m2·s·Pa), ensuring a higher gas separation throughput under higher temperatures. This study paves the way toward large-scale production and application of GO membranes as promising gas separation materials.

Mixed matrix membranes containing metal–organic frameworks were fabricated for pre-combustion CO2 capture.

Increasing attention has been given to nanobiocatalysis for commercial applications. In this study, laccase was immobilized on polyacrylonitrile (PAN) nanofibrous membranes through ethanol/HCl method of amidination reaction and successfully applied for removal of 2,4,6-trichlorophenol (TCP) from water. PAN membranes with fiber diameters from 200 nm to 300 nm were fabricated via electrospinning and provided a large surface area for enzyme immobilization and catalytic reactions. Images of scanning electron microscope demonstrated the enzyme molecules were aggregated on the nanofiber surface. The immobilized laccase exhibited 72% of the free enzyme activity and kept 60% of its initial activity after 10 operation cycles. Moreover, the storage stability of the immobilized laccase was considered excellent because they maintained more than 92% of the initial activity after 18 days of storage, whereas the free laccase retained only 20%. The laccase-PAN nanofibrous membranes exhibited high removal efficiency of TCP under the combined actions of biodegradation and adsorption. More than 85% of the TCP was removed under optimum conditions. Effects of various factors on TCP removal efficiency of the immobilized laccase were analyzed. Results suggest that laccase-PAN nanofibrous membranes can be used in removing TCP from aqueous sources and have potential for use in other commercial applications.

The surface free energy is one of the most fundamental properties of solids, hence, manipulating the surface energy and thereby the wetting properties of solids, has tremendous potential for various physical, chemical, biological as well as industrial processes. Typically, this is achieved by either chemical modification or by controlling the hierarchical structures of surfaces. Here we report a phenomenon whereby the wetting properties of vermiculite laminates are controlled by the hydrated cations on the surface and in the interlamellar space.We find that by exploiting this mechanism, vermiculite laminates can be tuned from superhydrophillic to hydrophobic simply by exchanging the cations; hydrophilicity decreases with increasing cation hydration free energy, except for lithium. Lithium, which has a higher hydration free energy than potassium, is found to provide a superhydrophilic surface due to its anomalous hydrated structure at the vermiculite surface. Building on these findings, we demonstrate the potential application of superhydrophilic lithium exchanged vermiculite as a