Impact of Cations and Framework on Trapdoor Behavior: A Study of Dynamic and In Situ Gas Analysis.

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 H2 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.

Ternary heterogeneous Z-scheme photocatalyst TiO2/CuInS2/OCN incorporated with carbon quantum dots (CQDs) for enhanced photocatalytic degradation efficiency of reactive yellow 145 dye in water.

This study delves into the advanced integration of a ternary heterogeneous Z-scheme photocatalyst, TiO2/CuInS2/OCN (OCN: O-g-C3N4), with carbon quantum dot (CQD) to improve the degradation efficiency of reactive yellow 145 (RY145) dye in water. Through a systematic examination, we elucidated the photocatalytic mechanisms and the role of radicals, electrons, and holes in the treatment process. Our findings revealed that this novel catalyst integration significantly boosted RY145 degradation efficiency, achieving 98.2%, which is markedly higher than the efficiencies which could be achieved using TiO2/CuInS2/OCN alone. Moreover, the TiO2/CuInS2/OCN/CQD photocatalyst demonstrated superior rate performance over its components. Comprehensive evaluations, including photoelectrochemical and radical tests, further confirmed the efficiency of the integrated system, adhering to Z-scheme principles. The catalyst showcased remarkable stability, with over 94% reusability after five reaction cycles. These findings pave the way for the potential use of the TiO2/CuInS2/OCN/CQD photocatalyst as an innovative solution for water pollutant treatment via photocatalytic technology.

Exploring the potential of ZnO-Ag@AgBr/SBA-15 Z-scheme heterostructure for efficient wastewater treatment: synthesis, characterization, and real-world applications.

This study reports on the synthesis and characterization of ZnO-Ag@AgBr/SBA-15 composites using natural halloysite clay from Yenbai Province, Vietnam, as a silica aluminum source. The synthesized materials demonstrated visible light absorption with a band gap energy range of 2.63-2.98 eV. The dual Z-scheme ZnO-Ag@AgBr/SBA-15 heterojunction exhibited superior catalytic performance compared to ZnO/SBA-15 and Ag@AgBr/SBA-15, owing to its improved electron transfer and reduced electron and hole recombination rate. In particular, the photocatalytic efficiency of ZnO-Ag@AgBr/SBA-15 was evaluated for the removal of harmful phenol red from wastewater under visible light irradiation. The photocatalytic process was optimized by varying the phenol red concentration, pH, and catalyst dosage, and showed that 98.8% of phenol red in 100 mL wastewater (pH = 5.5) can be removed using 40 mg of 20%ZnO-Ag@AgBr/SBA-15 within 120 min. Furthermore, the degradation pathway of phenol red was predicted using liquid chromatographic-mass spectrometry (LC-MS). Finally, the photocatalytic process was successfully tested using water samples collected from the four main domestic waste sources in Hanoi, including the To Lich River, the Hong River, the Hoan Kiem Lake, and the West Lake, demonstrating the high potential of the ZnO-Ag@AgBr/SBA-15 photocatalyst for phenol red degradation in real-world wastewater treatment applications.

Synthesis of porous high-temperature superconductors via a melamine formaldehyde sacrificial template.

Nanostructured high-temperature superconductors YBa2Cu3O6+δ and Bi2Sr2CaCu2O8+δ were synthesised using a melamine formaldehyde sponge as a sacrificial template, via three solution-based approaches. In the case of YBa2Cu3O6+δ , a modified Pechini method produced a material with a superconducting transition at 92 K and a specific surface area of 4.22 m2 g-1. Further analysis with Hg porosimetry determined that the sponge exhibited a porosity of 82%. In the case of Bi2Sr2CaCu2O8+δ , this method produced a material that exhibited superconductivity at 86 K with a specific surface area of 9.62 m2 g-1. Hg-porosimetry determined that the BSCCO sponge exhibited a porosity of 78%.

Designing a novel heterostructure AgInS2@MIL-101(Cr) photocatalyst from PET plastic waste for tetracycline degradation.

Semiconductor-containing porous materials with a well-defined structure could be unique scaffolds for carrying out selective organic transformations driven by visible light. We herein introduce for the first time a heterostructure of silver indium sulfide (AgInS2) ternary chalcogenide and a highly porous MIL-101(Cr) metal-organic framework (MOF) synthesised from polyethylene terephthalate plastic waste. Our results demonstrate that AgInS2 nanoparticles were uniformly attached to each lattice plane of the octahedral MIL-101(Cr) structure, resulting in a nanocomposite with a high distribution of semiconductors in a porous media. We also demonstrate that the nanocomposite with up to 40% of AgInS2 doping exhibited excellent catalytic activity for tetracycline degradation under visible light irradiation (∼99% tetracycline degraded after 4 h) and predominantly maintained its performance after five cycles. These results could promote a new material circularity pathway to develop new semiconductors that can be used to protect water from further pollution.

Improved photodegradation of anionic dyes using a complex graphitic carbon nitride and iron-based metal-organic framework material.

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.

Heterostructure of vanadium pentoxide and mesoporous SBA-15 derived from natural halloysite for highly efficient photocatalytic oxidative desulphurisation.

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 (V2O5) and mesoporous SBA-15 using inexpensive halloysite clay as the silica-aluminium source. The composite material with 40% doped V2O5 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.

Inclusion and release of ant alarm pheromones from metal-organic frameworks.

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.

Defective hierarchical porous copper-based metal-organic frameworks synthesised via facile acid etching strategy.

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.

Hierarchical Metal-Organic Frameworks with Macroporosity: Synthesis, Achievements, and Challenges.

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 CO2, 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.