This study first develops a facile method to synthesize zeolitic imidazolate framework cuboid (ZIF-C) nanosheets with tunable thickness from 70 to 170 nm from aqueous polymer solutions. The obtained ...ZIF-C nanosheets were characterized by various techniques, including X-ray diffractometry (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), N2 adsorption and thermogravimetric analysis (TGA), to understand their compositional and structural properties. The synthesized ZIF-Cs nanosheets with different thicknesses were further applied as nanofillers to prepare Pebax-based mixed matrix membranes (MMMs) to study the effect of the morphology on membrane properties and CO2/N2 separation performances under different relative humidity (RH) conditions. Results reveal that the incorporation of these ZIF-Cs simultaneously enhances CO2 permeability and CO2/N2 selectivity in the mixed matrix membranes. In addition, MMMs with the thickest ZIF-C nanosheet present better performance. A CO2 permeability of 387.2 Barrer accompanied with a CO2/N2 selectivity of 47.1 has been documented, nearly doubled in CO2 permeability with slightly increased selectivity compared with membranes containing thinner nanosheets.
Metal-organic framework gels and monoliths Hou, Jingwei; Sapnik, Adam F; Bennett, Thomas D
Chemical science (Cambridge),
01/2020, Letnik:
11, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The synthesis of metal-organic frameworks (MOFs) has, to date, largely been in the form of crystalline powders. However, interest in different physical morphologies of this class of materials is ...growing. In this perspective, we provide an overview of the structure, properties and applications of MOF monoliths. In particular, we explore the complex synthetic landscapes associated with MOF crystallization and discuss the synthetic factors leading to the formation of MOF gels,
i.e.
the precursor to sol-gel MOF monoliths. Finally, we provide our thoughts on the future development of this field, and attempt to highlight the importance of the MOF gel state in the discovery of new functional materials.
This perspective links the synthesis of MOF Gels to the formation of MOF-monoliths and their resultant properties and application.
Bio-catalytic degradation of recalcitrant micropollutants with enzymes such as laccase provides an environmentally attractive alternative to the conventional filtration and adsorption processes. ...However, enzyme loss and denaturation remain key challenges for their potential use in water treatment applications. In this work, laccase immobilization on TiO2 nanoparticles and TiO2 blended polyethersulfone (PES) membranes were investigated due to TiO2's chemical stability, ease of functionalization, and architecture. Different surface modification and functionalization strategies on support materials were compared based on enzyme loading, apparent activity, activity recovery, and stability. When coupling agent 3-aminopropyltriethoxysilane (APTES) and cross-linker glutaraldehyde (GLU) were applied sequentially, effective coupling of laccase was achieved based on 2,2′-azino-bis-(3-ethyl benzothiazoline-6-sulfonic acid) (ABTS) assays. TiO2 functionalized PES membrane showed better enzyme immobilization efficiency than the non-functionalized membrane. Optimal performance was observed for PES membrane containing 4wt% TiO2, where TiO2 not only provided the enzyme coupling sites but also affected the membrane surface morphology and hydrophilicity to favor the enzyme immobilization. These bio-catalytic membranes also displayed good enzyme stability, tolerance to wider pH range and vigorous filtration conditions required for water treatment applications. Kinetic study also indicated that the enzyme affinity to assay substrate was maintained after immobilization when compared with packed bed and batch reactors.
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•Laccase is immobilized on TiO2 nanoparticles and TiO2 functionalized membranes.•TiO2 loading has significant effect on bio-catalytic membrane performance.•Bio-catalytic membrane stability is mainly determined by immobilization technique.•Laccase on membrane has higher affinity to ABTS than batch and packed bed reactors.
Janus membranes are an emerging class of materials having opposing properties at an interface. This structure results in selective and often novel transport characteristics. In this Minireview, a ...definition of the Janus membrane, beyond merely asymmetric materials, is introduced and common fabrication strategies are outlined. Also presented are current and potential applications in directional transport, switchable permeation, and performance optimization with detailed mechanisms.
Crossing over: Janus membranes have received widespread interest over the past years. In this Minireview, a special definition of a Janus membrane is proposed and common fabrication methods of such membranes are outlined. Also summarized are the current and potential applications of Janus membranes in directional transport, switchable permeation, and performance optimization.
Biofouling is an inevitable obstacle that impairs the overall performance of polymeric membranes, including selectivity, permeability, and long-term stability. With an increase of various biocides ...being utilized to inhibit biofilm formation, the enhancement of bacterial resistance against traditional bactericides is increasingly becoming an extra challenge in the development of antimicrobial membranes. Graphene-based nanomaterials are emerging as a new class of strong antibacterial agents due to their oxygen-containing functional groups, sharp edges of the one-atom-thick laminar structure, and synergistic effect with other biocides. They have been successfully employed not only to confer favorable antibacterial abilities, but also to impart superior separation properties to polymeric membranes. However, the exact bactericidal mechanism of graphene remains unclear. This review aims to examine the synthesis methods and antimicrobial behavior of graphene-based materials, offering an insight into how the nanocomposites influence their antimicrobial abilities. Most importantly, the use of graphene-based nanomaterials in the design and development of antimicrobial membranes is highlighted.
Graphene-based nanocomposites have been increasingly used for the design of antimicrobial polymeric membranes due to enhanced antibacterial properties.
Surface zwitterionization of graphene oxide (GO) was firstly conducted by grafting poly(sulfobetaine methacrylate) (PSBMA) onto the GO surface via reverse atom transfer radical polymerization ...(RATRP). Then, a novel type of GO-PSBMA/polyethersulfone (PES) loose nanofiltration membrane (NFM) was constructed by mixing with modified GO composites via phase inversion. FTIR, XRD, TEM, XPS and TGA were applied to analyze the chemical composition and morphology, confirming a favorable synthesis of GO-PSBMA composites. Besides, the effect of the embedded GO-PSBMA nanoplates on the morphology and overall performance of the hybrid membranes was systematically investigated based on the SEM images, water contact angle, zeta potential, and fouling parameters. It was found that the water flux of the hybrid membrane was greatly enhanced from 6.44 L m-2 h-1 bar-1 to 11.98 L m-2 h-1 bar-1 when the GO-PSBMA content increased from 0 to 0.22 wt%. The antifouling tests revealed that the GO-PSBMA embedded membranes had an excellent antifouling performance: a high flux recovery ratio (ca. 94.4%) and a low total flux decline ratio (ca. 0.18). Additionally, the hybrid membranes exhibited a distinct advance in the mechanical strength due to the addition of highly rigid GO. Notably, compared with unmodified membranes, the hybrid membranes had a higher retention of Reactive Black 5 (99.2%) and Reactive Red 49 (97.2%), and a lower rejection of bivalent salts (10% for Na2SO4) at an operational pressure of 0.4 MPa, rendering the membranes promising for dye/salt fractionation.
Membranes are recognized as a key component in many environment and energy‐related applications, but conventional membranes are challenged to satisfy the growing demand for ever more energy‐efficient ...processes. Janus membranes, a novel class with asymmetric properties on each side, have recently emerged and represent enticing opportunities to address this challenge. With an inner driving force arising from their asymmetric configuration, Janus membranes are appealing for enhancing energy efficiency in a variety of membrane processes by promoting the desired transport. Here, the fundamental principles to prepare Janus membranes with asymmetric surface wettability and charges are summarized, and how they work in conventional and unconventional membrane processes is demonstrated.
The rise of Janus membranes brings new opportunities to tackle challenges surrounding energy management, while also enabling novel functions that are not even viable when using conventional membranes.
Geometric or electronic confinement of guests inside nanoporous hosts promises to deliver unusual catalytic or opto-electronic functionality from existing materials but is challenging to obtain ...particularly using metastable hosts, such as metal-organic frameworks (MOFs). Reagents (e.g. precursor) may be too large for impregnation and synthesis conditions may also destroy the hosts. Here we use thermodynamic Pourbaix diagrams (favorable redox and pH conditions) to describe a general method for metal-compound guest synthesis by rationally selecting reaction agents and conditions. Specifically we demonstrate a MOF-confined RuO
catalyst (RuO
@MOF-808-P) with exceptionally high catalytic CO oxidation below 150 °C as compared to the conventionally made SiO
-supported RuO
(RuO
/SiO
). This can be caused by weaker interactions between CO/O and the MOF-encapsulated RuO
surface thus avoiding adsorption-induced catalytic surface passivation. We further describe applications of the Pourbaix-enabled guest synthesis (PEGS) strategy with tutorial examples for the general synthesis of arbitrary guests (e.g. metals, oxides, hydroxides, sulfides).
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