Search

Clay–polymer nanocomposites (CPNs) containing a small weight fraction of nanoclay are known to display enhanced mechanical and thermal properties compared to neat polymers. However, the preparation and application of such nanocomposites remain challenging owing to the difficulties in dispersing nanoclays in polymer matrices. This study focuses on two surfactant-modified organophilic sepiolite clays to demonstrate the simplicity of the modification process, as well as on the use of a benzoxazine monomer (i.e., a CPN matrix precursor) itself as the modifier. Our in-house modified bespoke sepiolites achieve much better dispersion in a benzoxazine matrix, compared to the pristine clay, revealing their potential for applications as nanoenhancers for advanced composites. [ABSTRACT FROM AUTHOR]

Due to high surface area, loading capacity, and selectivity, Metal‐Organic Frameworks (MOFs) have shown much promise recently for potential applications in extraction and delivery of agrochemicals for environmental remediation and sustainable release, respectively. However, application of MOFs for pesticide delivery in wider agricultural context can be restricted by their granular form. Herein, an alternative approach is studied using biodegradable polymer‐MOF composites to address this limitation. The loading and release of a widely used pesticide, 2,4‐dichloropheoxycetic acid (2,4‐D), is studied using two MOFs, UiO‐66 and UiO‐66‐NH2, and the 2,4‐D‐loaded MOFs are incorporated into biodegradable polycaprolactone composites for convenient handling and minimizing runoff. The MOFs are loaded by in‐situ, and post‐synthetic methods, and characterised thoroughly to ensure successful synthesis and loading of 2,4‐D. The pesticide release studies are performed on the MOFs and composites in distilled water, and analysed using UV‐Vis spectroscopy, demonstrating sustained‐release of 2,4‐D over 16 days. The loaded MOF samples show high loading capacity, with up to 45 wt% for the in‐situ loaded UiO‐66. Release kinetics show more sustained release of 2,4‐D from UiO‐66‐NH2 compared to UiO‐66, which can be due to supramolecular interactions between the NH2 group of UiO‐66‐NH2 and 2,4‐D. This is further supported by computational studies. [ABSTRACT FROM AUTHOR]

Introducing heterostructures to graphitic carbon nitrides (g-C3N4) can improve the activity of visible-light-driven catalysts for the efficient treatment of multiple toxic pollutants in water. Here, we report for the first time that a complex material can be constructed from oxygen-doped g-C3N4 and a MIL-53(Fe) metal–organic framework using facile hydrothermal synthesis and recycled polyethylene terephthalate from plastic waste. The novel multi-walled nanotube structure of the O-g-C3N4/MIL-53(Fe) composite, which enables the unique interfacial charge transfer at the heterojunction, showed an obvious enhancement in the separation efficiency of the photochemical electron–hole pairs. This resulted in a narrow bandgap energy (2.30 eV, compared to 2.55 eV in O-g-C3N4), high photocurrent intensity (0.17 mA cm−2, compared to 0.12 mA cm−2 and 0.09 mA cm−2 in MIL-53(Fe) and O-g-C3N4, respectively) and excellent catalytic performance in the photodegradation of anionic azo dyes (95% for RR 195 and 99% for RY 145 degraded after 4 h, and only a minor change in the efficiency observed after four consecutive tests). These results demonstrate the development of new catalysts made from waste feedstocks that show high stability, ease of fabrication and can operate in natural light for environmental remediation. [ABSTRACT FROM AUTHOR]

Chabazite (CHA), one of the most common zeolite framework types, has a remarkable capacity to accommodate a wide range of different cations within the unique CHA framework. This has led to CHA being applied extensively in ion exchange, and studied for highly selective gas sorption, most notably through a trapdoor mechanism. Here, we report the systematic study of a series of six chabazite zeolites (i.e. K-CHA, Cs-CHA, Ca-CHA, Ba-CHA, Sr-CHA and Zn-CHA) obtained by subjecting the parent chabazite (KNa-CHA) to exchange operations with cations of different valences and atomic radii. These samples were examined using numerous techniques and it was found that the differences in valence and size between extra-framework cations exert a significant effect on the abundance of these cations positioned in the framework, resulting in differing nitrogen sorption ability measured in the synthesised chabazite zeolites. These findings will help to understand how the zeolite counter-cation affects the ability of the CHA material to selectively sequester and separate gases through the use of the trapdoor mechanism. [ABSTRACT FROM AUTHOR]

BACKGROUND The effect of framework topology on the guest‐induced flexibility of several crystalline zeolitic imidazolate frameworks (ZIF‐7, ZIF‐9, ZIF‐11 and ZIF‐12) was investigated via analysis of experimental nitrogen (N2), carbon dioxide (CO2) and argon (Ar) isotherms at 77 K (N2 and Ar) and 273 K (CO2) for gas pressures up to 0.13 MPa. RESULTS: The experimental isotherms of these frameworks were analysed in order to investigate their structural flexibility using gases with kinetic diameters equal to or larger than the diameters of their static pore apertures. The results of gas sorption measurements indicate guest‐induced phase changes for ZIF‐7 and ZIF‐9 (SOD topologies). ZIF‐12 (RHO topology) also shows uptake for gases, despite its pore‐limiting diameter being smaller than the kinetic diameters of the adsorbed molecules. CONCLUSIONS: This work highlights the ability of ZIFs with different framework topologies to change their structure and increase their pore aperture upon interaction with certain gases. These findings are key in the development of more selective ZIF‐based materials for important industrial applications including low‐energy gas separations, catalytic nanoreactors and sensor technology. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This work demonstrates the potential of zeolite Y supported nickel phosphide materials as highly active catalysts for the upgrading of bio-oil as an improved alternative to noble metal and transition metal sulphide systems. Our systematic work studied the effect of using different counterions (NH4+, H+, K+ and Na+) and Si/Al ratios (2.56 and 15) of the zeolite Y. It demonstrates that whilst the zeolite counterion itself has little impact on the catalytic activity of the bare Y-zeolite, it has a strong influence on the activity of the resulting nickel phosphide catalysts. This effect is related to the nature of the nickel phases formed during the synthesis process Zeolites containing K+ and Na+ favour the formation of a mixed Ni12P5/Ni2P phase, H+ Y produces both Ni2P and metallic Ni, whereas NH4+ Y produces pure Ni2P, which can be attributed to the strength of the phosphorus–aluminium interaction and the metal reduction temperature. Using quinoline as a model for the nitrogen-containing compounds in bio-oils, it is shown that the hydrodenitrogenation activity increases in the order Ni2P ＞ Ni0 ＞ Ni12P5. While significant research has been dedicated to the development of bio-oils produced by thermal liquefaction of biomass, surprisingly little work has been conducted on the subsequent catalytic upgrading of these oils to reduce their heteroatom content and enable processing in conventional petrochemical refineries. This work provides important insights for the design and deployment of novel active transition metal catalysts to enable the incorporation of bio-oils into refineries. [ABSTRACT FROM AUTHOR]

Three highly porous Zr(iv)-based metal–organic frameworks, UBMOF-8, UBMOF-9, and UBMOF-31, were synthesized by using 2,2′-diamino-4,4′-stilbenedicarboxylic acid, 4,4′-stilbenedicarboxylic acid, and combination of both linkers, respectively. The mixed-linker UBMOF-31 showed excellent hydrogen uptake of 4.9 wt% and high selectivity for adsorption of CO2 over N2 with high thermal stability and moderate water stability with permanent porosity and surface area of 2552 m2 g−1. [ABSTRACT FROM AUTHOR]

We report a facile biomimetic sol-gel synthesis using the sponge phase formed by the lipid monoolein as a structure-directing template, resulting in high phase purity, mesoporous dysprosium- and gadolinium titanates. The stability of monoolein in a 1,4-butanediol and water mixture complements the use of a simple sol-gel metal oxide synthesis route. By judicious control of the lipid/solvent concentration, the sponge phase of monoolein can be directly realised in the pyrochlore material, leading to a porous metal oxide network with an average pore diameter of 10 nm. [ABSTRACT FROM AUTHOR]

Improvements in the efficiency of combustion within a vehicle can lead to reductions in the emission of harmful pollutants and increased fuel efficiency. Gas sensors have a role to play in this process, since they can provide real time feedback to vehicular fuel and emissions management systems as well as reducing the discrepancy between emissions observed in factory tests and ‘real world’ scenarios. In this review we survey the current state-of-the-art in using porous materials for sensing the gases relevant to automotive emissions. Two broad classes of porous material – zeolites and metal–organic frameworks (MOFs) – are introduced, and their potential for gas sensing is discussed. The adsorptive, spectroscopic and electronic techniques for sensing gases using porous materials are summarised. Examples of the use of zeolites and MOFs in the sensing of water vapour, oxygen, NOx, carbon monoxide and carbon dioxide, hydrocarbons and volatile organic compounds, ammonia, hydrogen sulfide, sulfur dioxide and hydrogen are then detailed. Both types of porous material (zeolites and MOFs) reveal great promise for the fabrication of sensors for exhaust gases and vapours due to high selectivity and sensitivity. The size and shape selectivity of the zeolite and MOF materials are controlled by variation of pore dimensions, chemical composition (hydrophilicity/hydrophobicity), crystal size and orientation, thus enabling detection and differentiation between different gases and vapours. [ABSTRACT FROM AUTHOR]