Thermo‐Driven Controllable Emulsion Separation by a Polymer‐Decorated Membrane with Switchable Wettability

A thermoresponsive Poly(N‐isopropylacrylamide) (PNIPAAm)‐modified nylon membrane was fabricated via hydrothermal route. Combining rough structure, proper pore size, and thermoresponsive wettability, the membrane can separate at least 16 types of stabilized oil‐in‐water and water‐in‐oil emulsions at different temperatures. Below the LCST (ca. 25 °C), the material exhibits hydrophilicity and underwater superoleophobicity, which can be used for the separation of various kinds of oil‐in‐water emulsions. Above the LCST (ca. 45 °C), the membrane shows the opposite property with high hydrophobicity and superoleophilicity, and it can then separate stabilized water‐in‐oil emulsions. The material exhibits excellent recyclability and high separation efficiency for various kinds of emulsions and the hydrothermal method is facile and low‐cost. The membrane shows good potential in real situations such as on‐demand oil‐spill cleanup, industrial wastewater treatment, remote operation of oil/water emulsion separation units, and fuel purification.     

A Scalable Chemical Approach for the Synthesis of a Highly Tolerant and Efficient Oil Absorbent

In the past, bio‐inspired extreme water repellent property has been strategically embedded on commercially available sponges for developing selective oil absorbents. However, most of the reported materials lack physical and chemical durability, limiting their applicability at practically harsh settings. Herein, a stable dispersion of polymeric nanocomplexes was exploited to achieve a chemically reactive coating on the highly compressible melamine foam. A superhydrophobic melamine foam (SMF) was achieved after post‐covalent modification of the reactive coating through 1,4‐conjugate addition reaction at ambient conditions. The durability of the embedded extreme water repellent property in the as‐modified melamine foam has been elaborately demonstrated through exposing it to severe physical manipulations, chemically harsh aqueous media including pH 1, pH 12, surfactant contaminated water, river water, seawater and prolonged UV irradiation. Thus, the highly tolerant SMF was utilized as an efficient oil absorbent wherein oils of varying densities could be selectively recovered from an oil/water interface with high (e.g., 137 g g^?1 for chloroform and 83 g g^?1 for diesel) oil absorption capacity. Moreover, the selective oil absorption capacity of the as‐synthesized material remained unaffected at practically relevant severe chemical and physical settings, and the extreme water repellency of the material remained unaltered even after repetitive (at least 50 cycles) use for oil/water separation.     

Proton Transport in a Highly Conductive Porous Zirconium‐Based Metal–Organic Framework: Molecular Insight

The water stable UiO‐66(Zr)‐(CO₂H)₂ MOF exhibits a superprotonic conductivity of 2.3×10^?3 S cm^?1 at 90 °C and 95 % relative humidity. Quasi‐elastic neutron scattering measurements combined with aMS‐EVB3 molecular dynamics simulations were able to probe individually the dynamics of both confined protons and water molecules and to further reveal that the proton transport is assisted by the formation of a hydrogen‐bonded water network that spans from the tetrahedral to the octahedral cages of this MOF. This is the first joint experimental/modeling study that unambiguously elucidates the proton‐conduction mechanism at the molecular level in a highly conductive MOF.     

Synthesis of a metal–organic framework confined in periodic mesoporous silica with enhanced hydrostability as a novel fiber coating for solid‐phase microextraction

A metal–organic framework/periodic mesoporous silica (MOF‐5@SBA‐15) hybrid material has been prepared by using SBA‐15 as a matrix. The prepared MOF‐5@SBA‐15 hybrid material was then deposited on a stainless‐steel wire to obtain the fiber for the solid‐phase microextraction of phenolic compounds. Modifications in the metal–organic framework structure have proven to improve the extraction performance of MOF/SBA‐15 hybrid materials, compared to pure MOF‐5 and SBA‐15. Optimum conditions include an extraction temperature of 75°C, a desorption temperature of 260°C, and a salt concentration of 20% w/v. The dynamic linear range and limit of detection range from 0.1–500 and from 0.01–3.12 ng/mL, respectively. The repeatability for one fiber (n = 3), expressed as relative standard deviation, is between 4.3 and 9.6%. The method offers the advantage of being simple to use, rapid, and low cost, the thermal stability of the fiber, and high relative recovery (compared to conventional methods) represent additional attractive features.     

Coordination‐Driven In Situ Self‐Assembly Strategy for the Preparation of Metal–Organic Framework Hybrid Membranes

Metal–organic frameworks (MOFs) have emerged as porous solids of a superior type for the fabrication of membranes. However, it is still challenging to prepare a uniformly dispersed robust MOF hybrid membrane. Herein, we propose a simple and powerful strategy, namely, coordination‐driven in situ self‐assembly, for the fabrication of MOF hybrid membranes. On the basis of the coordination interactions between metal ions and ligands and/or the functional groups of the organic polymer, this method was confirmed to be feasible for the production of a stable membrane with greatly improved MOF‐particle dispersion in and compatibility with the polymer, thus providing outstanding separation ability. As an experimental proof of concept, a high‐quality ZIF‐8/PSS membrane was fabricated that showed excellent performance in the nanofiltration and separation of dyes from water.     

Preparation of emulsion‐templated fluorinated polymers and their application in oil/water separation

A series of emulsion‐templated fluorinated polymers (polyHIPEs) were first synthesized with introducing 2‐(perfluorohexyl)ethyl methacrylate (PEM) to the external phase of water‐in‐styrene high internal phase emulsion (HIPE) templates. The morphology (i.e., void size and its distribution) of these porous materials could be tuned simply by changing PEM and/or surfactant amount. The synergistic effect between the surface chemistry and surface architecture allowed the polyHIPEs to possess hydrophobicity with a water contact angle of 151°. The superhydrophobicity and oleophilicity of the polyHIPEs, together with their highly open porous structure, make the material a very competitive candidate as a filtration material for oil/water separation in practice with the efficiency of separating dichloromethane from the oil/water mixture of 95%. Such oil/water separating capacity was maintained after 10 cycles of filtration of oil/water, indicating the cyclic usage of the polyHIPE is feasible. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1508–1515     

Preparation and characterization of ZIF-8 and ZIF-67 incorporated poly(vinylidene fluoride) membranes for pervaporative separation of methanol/water mixtures

Metal–organic frameworks (MOFs) are made up of metal centers and organic binders with larger surface area and distinct pore structures. Particularly significant advancement in MOF membranes has been achieved in three different directions: preparation of MOF membranes with larger surface area, improving the membrane performance by surface modification, and its usage with added features. However, its significance has not been completely known and concluded yet. MOF membranes are used in a variety of membrane-based separation like gas permeation, nanofiltration, pervaporation, membrane distillation, etc. This research aims to synthesize MOFs (ZIF-8 and ZIF-67) and MOF membranes (ZIF-8/PVDF and ZIF-67/PVDF) and used them in the pervaporative separation of the methanol/water mixture. MOFs and MOF membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and thermogravimetry analysis. Methanol/water mixtures were be used to study the performance of the prepared membranes. A study on the process parameters such as temperature (40, 45, 50, and 55°C), feed pressure (4, 8, 12, and 16 psi), and feed composition (10%, 20%, 30%, and 40% of water) was carried out to examine the effect of each process parameters for pure membrane. In contrast, Taguchi screening design was used to screen the most influential process variable. The optimized conditions based on Taguchi screening method were 55°C, 12 psi, and 40 %vol of water in feed. The obtained total flux of 425 L/m²h was observed for M3 membrane. As feed temperature increased, the total flux of all three membranes was increased.     

Robust Superhydrophobic/Superoleophilic Wrinkled Microspherical MOF@rGO Composites for Efficient Oil–Water Separation

Graphene/MOF‐based composite materials in three‐dimensional (3D) architectures are promising for the treatment of oil‐containing wastewater by absorption owing to their intrinsic properties of graphene and metal‐organic frameworks (MOFs), such as high porosity, ultralow density, and facilely tailored superwettability. In this study, novel wrinkled 3D microspherical MOF@rGO composites with both superhydrophobic and superoleophilic properties were developed by embedding MOF nanoparticles between graphene oxide (GO) nanosheets, followed by high‐temperature reduction self‐assembly. The microspherical composites feature a unique micro/nano hierarchy consisting of crumpled reduced GO (rGO) nanosheets intercalated with well‐dispersed MOF nanoparticles. Combined with the superwettability and abundant meso/microporosity, the peculiar architectures of wrinkled ZIF‐8@rGO microspheres show very fast absorption rates and high sorption selectivity for organic solvents and oils from water.     

Electrospun N‐Substituted Polyurethane Membranes with Self‐Healing Ability for Self‐Cleaning and Oil/Water Separation

Membranes with special functionalities, such as self‐cleaning, especially those for oil/water separation, have attracted much attention due to their wide applications. However, they are difficult to recycle and reuse after being damaged. Herein, we put forward a new N‐substituted polyurethane membrane concept with self‐healing ability to address this challenge. The membrane obtained by electrospinning has a self‐cleaning surface with an excellent self‐healing ability. Importantly, by tuning the membrane composition, the membrane exhibits different wettability for effective separation of oil/water mixtures and water‐in‐oil emulsions, whilst still displaying a self‐healing ability and durability against damage. To the best of our knowledge, this is the first report to demonstrate a self‐healing membrane for oil/water separation, which provides the fundamental research for the development of advanced oil/water separation materials.     

Wettability alteration of carbonate rocks from strongly liquid-wetting to strongly gas-wetting by fluorine-doped silica coated by fluorosilane

Wettability alteration is an important mechanism to increase recovery from oil and gas reservoirs. In this study, effect of fluorine-doped silica coated by fluorosilane nanofluid on wettability alteration of carbonate rock was investigated. The nanoparticle synthesized by sol-gel method was characterized using XRD, FTIR, SEM, and DLS. Adsorption of nanoparticle on rock was characterized by FESEM, and composition of rock after treatment was determined by EDXA. Effect of nanofluid on wettability was investigated by measuring static, advancing, and receding contact angle and surface free energy, imbibition of water, crude oil, and condensate of untreated and treated carbonate rock. Also, stability of contact angle and thermal stability of nanofluid were studied. ?Results show that contact angles for water, condensate, and crude oil were altered from 37.95°, 0°, ?and 0° to 146.47°, 145.59°, and 138.24°. In addition, water, condensate, and oil imbibition ?decreased more than 87, 88, and 80%, indicating that wettability was altered from strongly oil wet, ?condensate wet, and water wet to strongly gas wet. The ultraoleophobic and ultrahydrophobic stability were >48 hours and 120 minutes. Surface free energy of treated rock for water, crude oil, and condensate was ?2.24, 1.17, and 1.47mN/m. Thermal stability of nanofluids and adsorbed nanoparticle was up to 150°C.     

Microporous 3D aluminum MOF doped into chitosan‐based mixed matrix membranes for ethanol/water separation

An aluminum metal–organic framework (Al‐MOF), [Al(OH)(BPDC)] (DUT‐5; BPDC = Biphenyl‐4,4′‐dicarboxylate), was synthesized using solvothermal reactions. The high surface area and micropores (approximately 1.2 nm) of DUT‐5 were characterized using N₂ gas sorption measurements. The thermal stability of DUT‐5 and its phase purity were also investigated. The different amounts of DUT‐5 (0.1, 0.15, and 0.2 wt%) were successfully incorporated into the chitosan (CS) polymer to prepare a mixed matrix membrane (MMM) for the pervaporation of water/ethanol at 25°C. In particular, when 0.15 wt% of DUT‐5 was loaded, the DUT‐5@CS MMMs displayed excellent permeability and selectivity in ethanol/water separation. The results indicated that compared with pristine chitosan membranes, the flux of DUT‐5@CS membranes with 0.15 wt% loading significantly increased from 315 to 378 (g/m² h^?1) and the separation factor from 347 to 3,429. These promising results of the microporous Al‐MOF doped into chitosan MMMs reveal its good application potential for the bio‐ethanol separation processes.     

Interactive Thermal Effects on Metal–Organic Framework Polymer Composite Membranes

Polymeric membranes are important tools for intensifying separation processes in chemical industries, concerning strategic tasks such as CO₂ sequestration, H₂ production, and water supply and disposal. Mixed‐matrix and supported membranes have been widely developed; recently many of them have been based on metal–organic frameworks (MOFs). However, most of the impacts MOFs have within the polymer matrix have yet to be determined. The effects related to thermal behavior arising from the combination of MOF ZIF‐8 and polysulfone have now been quantified. The catalyzed oxidation of the polymer is strongly affected by the MOF crystal size and distribution inside the membrane. A 16 wt % 140 nm‐sized ZIF‐8 loading causes a 40 % decrease in the observed activation energy of the polysulfone oxidation that takes place at a temperature (545 °C) 80 °C lower than in the raw polymer (625 °C).     

Ruthenium Complexation in an Aluminium Metal–Organic Framework and Its Application in Alcohol Oxidation Catalysis

A ruthenium trichloride complex has been loaded into an aluminium metal–organic framework (MOF), MOF‐253, by post‐synthetic modification to give MOF‐253‐Ru. MOF‐253 contains open bipyridine sites that are available to bind with the ruthenium complex. MOF‐253‐Ru was characterised by elemental analysis, N₂ sorption and X‐ray powder diffraction. This is the first time that a Ru complex has been coordinated to a MOF through post‐synthetic modification and used as a heterogeneous catalyst. MOF‐253‐Ru catalysed the oxidation of primary and secondary alcohols, including allylic alcohols, with PhI(OAc)₂ as the oxidant under very mild reaction conditions (ambient temperature to 40 °C). High conversions (up to >99 %) were achieved in short reaction times (1–3 h) by using low catalyst loadings (0.5 mol % Ru). In addition, high selectivities (>90 %) for aldehydes were obtained at room temperature. MOF‐253‐Ru can be recycled up to six times with only a moderate decrease in substrate conversion.     

Preparation of hierarchically structured PCL superhydrophobic membrane via alternate electrospinning/electrospraying techniques

Superhydrophobic polycaprolactone (PCL) membranes with hierarchical structure were fabricated via alternate electrospinning/electrospraying techniques. Electrospun PCL/methyl silicone oil (PCL/MSO) nanofibers were employed as substrate. PCL/MSO‐PCL microspheres (PCL/MSO‐PCL_MS) hierarchical membrane was prepared via electrosprayed PCL_MS as an additional layer on the substrate. Field emission scanning electron microscopy images showed the formation of hierarchical PCL/MSO‐PCL_MS membranes. Compared to pure PCL fibers substrate (120 ± 1.3°), the water contact angle (WCA) of MSO‐modified PCL membrane was 142 ± 0.7°. The most interesting observation was that the WCA of PCL_MS without any modification could be achieved to 146 ± 2.8°. On this basis, PCL/MSO‐PCL_MS hierarchical membrane possessed superhydrophobic surface with 150 ± 0.6° of WCA. The excellent surface roughness and air‐pocket capacity of hierarchical membranes would make the membranes more hydrophobic. The maximum oil (n‐hexane) adsorption capacity of PCL/MSO‐PCL_MS membrane was 32.53 g g^?1. Oil–water separation efficiencies of the superhydrophobic membranes were all higher than 99.93% after 10 cycles. The hierarchically structured PCL superhydrophobic membranes indicate the potential applications of environmentally friendly biopolymers as separation membranes. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 421–430     

Highly Selective Water Adsorption in a Lanthanum Metal–Organic Framework

We present a new metal–organic framework (MOF) built from lanthanum and pyrazine‐2,5‐dicarboxylate (pyzdc) ions. This MOF, [La(pyzdc)_1.5(H₂O)₂] ? 2 H₂O, is microporous, with 1D channels that easily accommodate water molecules. Its framework is highly robust to dehydration/hydration cycles. Unusually for a MOF, it also features a high hydrothermal stability. This makes it an ideal candidate for air drying as well as for separating water/alcohol mixtures. The ability of the activated MOF to adsorb water selectively was evaluated by means of thermogravimetric analysis, powder and single‐crystal X‐ray diffraction and adsorption studies, indicating a maximum uptake of 1.2 mmol g^?1 MOF. These results are in agreement with the microporous structure, which permits only water molecules to enter the channels (alcohols, including methanol, are simply too large). Transient breakthrough simulations using water/methanol mixtures confirm that such mixtures can be separated cleanly using this new MOF.     

原位配体功能化策略制备共价金属有机骨架促进其析氢反应

新型多孔材料在诸多领域具有广阔的应用前景,其发展引起了研究者较大关注.在过去的十年中,大量的先进多孔材料被设计并应用于不同领域.其中,共价有机骨架(COFs)和金属有机骨架(MOFs)材料由于具有结构多样、孔隙可调以及功能多样等独特性质,得到了广泛研究.为了有效地结合各个组分的优点以获得最优性能,科研工作者投入了大量的...     

A Methylthio‐Functionalized‐MOF Photocatalyst with High Performance for Visible‐Light‐Driven H2 Evolution

Recently, the emergence of photoactive metal–organic frameworks (MOFs) has given great prospects for their applications as photocatalytic materials in visible‐light‐driven hydrogen evolution. Herein, a highly photoactive visible‐light‐driven material for H₂ evolution was prepared by introducing methylthio terephthalate into a MOF lattice via solvent‐assisted ligand‐exchange method. Accordingly, a first methylthio‐functionalized porous MOF decorated with Pt co‐catalyst for efficient photocatalytic H₂ evolution was achieved, which exhibited a high quantum yield (8.90 %) at 420 nm by use sacrificial triethanolamine. This hybrid material exhibited perfect H₂ production rate as high as 3814.0 μmol g^?1 h^?1, which even is one order of magnitude higher than that of the state‐of‐the‐art Pt/MOF photocatalyst derived from aminoterephthalate.     

Modular Customization and Regulation of Metal–Organic Frameworks for Efficient Membrane Separations

Metal–organic frameworks (MOFs) are considered ideal membrane candidates for energy-efficient separations. However, the MOF membrane amount to date is only a drop in the bucket compared to the material collections. The fabrication of an arbitrary MOF membrane exhibiting inherent separation capacity of the material remains a long-standing challenge. Herein, we report a MOF modular customization strategy by employing four MOFs with diverse structures and physicochemical properties and achieving innovative defect-free membranes for efficient separation validation. Each membrane fully displays the separation potential according to the MOF pore/channel microenvironment, and consequently, an intriguing H₂/CO₂ separation performance sequence is achieved (separation factor of 1656–5.4, H₂ permeance of 964–2745 gas permeation unit). Taking advantage of this strategy, separation performance can be manipulated by a non-destructive modification separately towards the MOF module. This work establishes a universal full-chain demonstration for membrane fabrication-separation validation-microstructure modification and opens an avenue for exclusive customization of membranes for important separations.     

Biomimetic Superhydrophobic/Superoleophilic Highly Fluorinated Graphene Oxide and ZIF‐8 Composites for Oil–Water Separation

Superhydrophobic/superoleophilic composites HFGO@ZIF‐8 have been prepared from highly fluorinated graphene oxide (HFGO) and the nanocrystalline zeolite imidazole framework ZIF‐8. The structure‐directing and coordination‐modulating properties of HFGO allow for the selective nucleation of ZIF‐8 nanoparticles at the graphene surface oxygen functionalities. This results in localized nucleation and size‐controlled ZIF‐8 nanocrystals intercalated in between HFGO layers. The composite microstructure features fluoride groups bonded at the graphene. Self‐assembly of a unique micro‐mesoporous architecture is achieved, where the micropores originate from ZIF‐8 nanocrystals, while the functionalized mesopores arise from randomly organized HFGO layers separated by ZIF‐8 nanopillars. The hybrid material displays an exceptional high water contact angle of 162° and low oil contact angle of 0° and thus reveals very high sorption selectivity, fast kinetics, and good absorbencies for nonpolar/polar organic solvents and oils from water. Accordingly, Sponge@HFGO@ZIF‐8 composites are successfully utilized for oil–water separation.     

All‐Nanoporous Hybrid Membranes: Redefining Upper Limits on Molecular Separation Properties

New membrane‐based molecular separation processes are an essential part of the strategy for sustainable chemical production. A large literature on “hybrid” or “mixed‐matrix” membranes exists, in which nanoparticles of a higher‐performance porous material are dispersed in a polymeric matrix to boost performance. We demonstrate that the hybrid membrane concept can be redefined to achieve much higher performance if the membrane matrix and the dispersed phase are both nanoporous crystalline materials, with no polymeric phase. As the first example of such a system, we find that surface‐treated nanoparticles of the zeolite MFI can be incorporated in situ during growth of a polycrystalline membrane of the MOF ZIF‐8. The resulting all‐nanoporous hybrid membrane shows propylene/propane separation characteristics that exceed known upper‐bound performance limits defined for polymers, nanoporous materials, and polymer‐based hybrid membranes. This serves as a starting point for a new generation of chemical separation membranes containing interconnected nanoporous crystalline phases.