Integration between conventional semiconductors and porous materials can enhance electron-hole separation, improving photocatalytic activity. Here, we introduce a heterostructure that was ...successfully constructed between vanadium pentoxide (V
2
O
5
) and mesoporous SBA-15 using inexpensive halloysite clay as the silica-aluminium source. The composite material with 40% doped V
2
O
5
shows excellent catalytic performance in the oxidative desulphurisation of dibenzothiophene (conversion of 99% with only a minor change after four-cycle tests). These results suggest the development of new catalysts made from widely available natural minerals that show high stability and can operate in natural light to produce fuel oils with ultra-low sulphur content.
New and robust catalysts made from natural minerals that can operate in sunlight to produce fuel oils with ultra-low-sulphur content.
Display omitted
•Photocatalytic desulfurization was enhanced using Ag@AgBr nanoparticles doped in the mesoporous Al-SBA-15.•Light absorption expanded to the visible region for Ag@AgBr/Al-SBA-15 ...samples with various content of Ag@AgBr.•Sample with a 30% Ag@AgBr doping exhibited enhanced photocatalytic activity.
In recent decades, highly efficient deep desulfurization processes have become very necessary to decrease environmental pollution due to sulfur emissions from fuels. Herein, an enhanced photocatalytic desulfurization of a model fuel was investigated under sunlight irradiation using H2O2 as the oxidant and Ag@AgBr loaded mesoporous silica Al-SBA-15 as a catalyst. In this study, the photocatalyst (Ag@AgBr/Al-SBA-15) was synthesized via a chemical deposition using halloysite clay as the silica–aluminum source and characterized by X-ray diffraction, N2 adsorption, scanning electron microscopy, transmission electron microscopy, and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The UV–Vis DRS results revealed that the light absorption expanded to the visible region (λ>400nm) for the various Ag@AgBr nanoparticles doped in the mesoporous Al-SBA-15 material. The 30% Ag@AgBr/Al-SBA-15 sample with a 30% Ag@AgBr doping exhibited enhanced photocatalytic activity and showed high stability even after four successive cycles. The results demonstrated that initial dibenzothiophene concentrations (500ppm) reached 98.66% removal with 50mg of the catalyst dosage, 1.0mL of H2O2, for 360min of sunlight irradiation at 70°C.
Highlights
The advantages of macroporous metal–organic frameworks (MOFs) in comparison with micro- and mesoporous MOFs are discussed.
A range of synthetic methods for the fabrication and ...characterisation of hierarchical MOFs with macroporosity are reviewed.
The applications, advancements, and challenges of each method are compared and assessed in detail.
Introduction of multiple pore size regimes into metal–organic frameworks (MOFs) to form hierarchical porous structures can lead to improved performance of the material in various applications. In many cases, where interactions with bulky molecules are involved, enlarging the pore size of typically microporous MOF adsorbents or MOF catalysts is crucial for enhancing both mass transfer and molecular accessibility. In this review, we examine the range of synthetic strategies which have been reported thus far to prepare hierarchical MOFs or MOF composites with added macroporosity. These fabrication techniques can be either pre- or post-synthetic and include using hard or soft structural template agents, defect formation, routes involving supercritical CO
2
, and 3D printing. We also discuss potential applications and some of the challenges involved with current techniques, which must be addressed if any of these approaches are to be taken forward for industrial applications.
Introducing hierarchical pore structure to microporous materials such as metal-organic frameworks (MOFs) can be beneficial for reactions where the rate of reaction is limited by low rates of ...diffusion or high pressure drop. This advantageous pore structure can be obtained by defect formation, mostly via post-synthetic acid etching, which has been studied extensively on water-stable MOFs. Here we show that a water-unstable HKUST-1 MOF can also be modified in a corresponding manner by using phosphoric acid as a size-selective etching agent and a mixture of dimethyl sulfoxide and methanol as a dilute solvent. Interestingly, we demonstrate that the etching process which is time- and acidity- dependent, can result in formation of defective HKUST-1 with extra interconnected hexagonal macropores without compromising on the bulk crystallinity. These findings suggest an intelligent scalable synthetic method for formation of hierarchical porosity in MOFs that are prone to hydrolysis, for improved molecular accessibility and diffusion for catalysis.
Due to their distinct and tailorable internal cavity structures, zeolites serve as promising materials for efficient and specific gas separations such as the separation of /CO2 from N2. A subset of ...zeolite materials exhibits trapdoor behavior which can be exploited for particularly challenging separations, such as the separation of hydrogen, deuterium, and tritium for the nuclear industry. This study systematically delves into the influence of the chabazite (CHA) and merlinoite (MER) zeolite frameworks combined with different door-keeping cations (K + , Rb + , and Cs + ) on the trapdoor separation behavior under a variety of thermal and gas conditions. Both CHA and MER frameworks were synthesized from the same parent Y-zeolite and studied using in situ X-ray diffraction as a function of increasing temperatures under 1 bar H 2 exposures. This resulted in distinct thermal responses, with merlinoite zeolites exhibiting expansion and chabazite zeolites showing contraction of the crystal structure. Simultaneous thermal analysis (STA) and gas sorption techniques further demonstrated how the size of trapdoor cations restricts access to the internal porosities of the zeolite frameworks. These findings highlight that both the zeolite frameworks and the associated trapdoor cations dictate the thermal response and gas sorption behavior. Frameworks determine the crystalline geometry, the maximum porosities, and displacement of the cation in gas sorption, while associated cations directly affect the blockage of the functional sites and the thermal behavior of the frameworks. This work contributes new insights into the efficient design of zeolites for gas separation applications and highlights the significant role of the trapdoor mechanism.
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.
The differences in valence and size between extra-framework cations exert a significant effect on the nitrogen sorption ability in the synthesised chabazite zeolites (K-CHA, Cs-CHA, Ca-CHA, Ba-CHA, Sr-CHA and Zn-CHA).
Al-doped TiO
2
nanoparticles with different Al contents were prepared by a simple sol–gel method and were applied as UV filters for sunscreen products. These materials were characterized by XRD, ...Raman, FESEM, N
2
adsorption-desorption, WDXRF, FTIR, and UV–visible diffuse reflectance spectroscopy. Their color and photocatalytic activity were evaluated through CIE L*a*b* colorimetric method and the degradation of methylene blue under UV light, respectively. According to the results, the insertion of Al
3+
ions into TiO
2
successfully reduced the photocatalytic performance via the decrease in the mass fraction of rutile phase, the decrease in surface hydroxyl groups, and the increase in dislocation density. These Al-doped powders display better UV absorption than the undoped TiO
2
, which can be attributed to the increase in anatase content and the decrease in particle size due to Al-doping. Consequently, the sunscreen using 4 mol% Al-doped TiO
2
reveals the enhanced SPF value and improved color stability, which are suitable for UV protection cosmetics.
Graphical Abstract
Highlights
Preparation of Al-doped TiO
2
nanoparticles by sol-gel method.
Al-doping successfully reduces the photocatalytic activity of TiO
2
.
Al-doped TiO
2
nanoparticles show high UV absorption and bright ivory-white color.
Sunscreen using Al-doped TiO
2
display high SPF values and high color stability.
Al-doped TiO
2
nanoparticles can be safety used as UV filters in sunscreens.
This study demonstrates the sustainable synthesis of multifunctional CIS@MIL-101(Cr) composites for water treatment applications. The composites were prepared via hybridization of CuInS2 with ...MIL-101(Cr) resulting in the formation of CIS nanoplates incorporated into MIL-101(Cr). The composites exhibited enhanced visible light photocatalytic activity due to their low bandgap energy and were tested for tetracycline photodegradation achieving a degradation efficiency of 98.8%. The material showed high stability after four cycles, and the effects of reactive species on photodegradation were investigated. The kinetics and mechanism of the photocatalytic process were studied, and LC-MS analysis was conducted to identify intermediate products. These results demonstrate the potential of using waste PET to create new semiconductors for water pollution control, promoting a circular material pathway.
Zinc(
ii
) and zirconium(
iv
) metal-organic frameworks show uptake and slow release of the ant alarm pheromones 3-octanone and 4-methyl-3-heptanone. Inclusion of
N
-propyl groups on the MOFs allows ...for enhanced uptake and release over several months. In preliminary field trials, leaf cutting ants show normal behavioural responses to the released pheromones.
Zinc(
ii
) and zirconium(
iv
) MOFs show uptake and slow release of the ant alarm pheromones 3-octanone and 4-methyl-3-heptanone.
Introducing heterostructures to graphitic carbon nitrides (g-C
3
N
4
) 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-C
3
N
4
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-C
3
N
4
/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-C
3
N
4
), 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-C
3
N
4
, 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.
The heterojunction between a metal-organic framework and graphitic carbon nitride can form a novel porous structure which reduces the rate of electron-hole recombination, thus improving the photocatalytic performance of the composite for wastewater treatment.
PDF
