Ag nanoparticles supported on UiO-66 for selective oxidation of styrene

UiO-66 Inspired Superhydrophobic Coatings Fabricated from Discarded Polyester/Spandex Textiles

We report on a method for synthesizing superhydrophobic coatings using a UiO-66 metal-organic framework (MOF) with discarded polyester/Spandex fabrics as raw materials. Unlike traditional recycling techniques that involve separating non-poly(ethylene terephthalate) (PET) components, our approach directly uses blended polyester/Spandex fibers. Discarded polyester/Spandex fabrics were exposed to an alkaline depolymerization process to produce disodium terephthalate (Na2BDC), which is a known linker for UiO-66 synthesis. We conducted experiments under two different conditions involving different amounts of ethanol. We found that with a small amount of ethanol, the resulting UiO-66 structure, when assembled on top of a polyester/Spandex substrate, exhibited a water contact angle of ≥150°─a superhydrophobic behavior. When using larger amounts of ethanol, we noted a hydrophobic behavior with a water contact angle of ∼139°. As a control, we performed the same experiments but using discarded 100% polyester fabrics as raw materials, which resulted in a superhydrophilic behavior. We attribute the superhydrophobic behavior of the UiO-66 coatings, produced from the polyester/Spandex fabrics, to the presence of hydrophobic compounds generated by the chemical degradation of Spandex. Our approach introduces a pathway for upcycling discarded textiles into superhydrophobic coatings.

Cooperative and Bifunctional Adsorbent-Catalyst Materials for In-situ VOCs Capture-Conversion

Volatile organic compounds (VOCs) are gases that are emitted into the air from products or processes and are major components of air pollution that significantly deteriorate air quality and seriously affect human health. Different types of metals, metal oxides, mixed-metal oxides, polymers, activated carbons, zeolites, metal-organic frameworks (MOFs) and mixed-matrixed materials have been developed and used as adsorbent or catalyst for diversified VOCs detection, removal, and destruction. In this comprehensive review, we first discuss the general classification of VOCs removal materials and processes and outline the historical development of bifunctional and cooperative adsorbent-catalyst materials for the removal of VOCs from air. Subsequently, particular attention is devoted to design of strategies for cooperative adsorbent-catalyst materials, along with detailed discussions on the latest advances on these bifunctional materials, reaction mechanisms, long-term stability, and regeneration for VOCs removal processes. Finally, challenges and future opportunities for the environmental implementation of these bifunctional materials are identified and outlined with the intent of providing insightful guidance on the design and fabrication of more efficient materials and systems for VOCs removal in the future.

Development of a label-free impedimetric aptasensor based on Zr-MOF and titaniom carbide nanosheets for detection of L-tryptophan

This study primarily focuses on the L-Tryptophan (Trp) biomarker assay, with particular attention given to its objectives. The investigation centers on the potential implications of imbalanced Trp levels and its associated metabolites, which have been attributed to the spectrum of both psychological and physiological disorders, encompassing conditions such as cancer. Therefore, the swift and accurate detection of this amino acid is of paramount importance in cancer monitoring, as it plays a crucial role in preventing the metastasis and spread of cancer cells. Thus, an electrochemical aptasensor was designed based on nanocomposite of AgNPs@UiO-66/Ti3C2 (MXene) as immobilization strategy for the ultrasensitive detection of Trp. Zirconium metal-organic frameworks (Zr-MOFs) were employed as carriers for silver nanoparticles to facilitate subsequent binding with aptamers. Markedly, the obtained results show that the constructed aptasensor can specifically detect Trp in the two concentration range from 1fM to 1 nM and 1 nM to 200 nM and with a low detection limit of 0.35 fM. When applied to real samples, the experimental results demonstrated positive recovery rates. Consequently, a discerning and sensitive electrochemical aptasensor devoid of labeling agents was successfully fabricated for the explicit purpose of Trp detection.

Recent advances of metal-organic framework-based and derivative materials in the heterogeneous catalytic removal of volatile organic compounds

Since the environmental hazards of volatile organic compounds (VOCs) are well known, heterogeneous catalysis has become one of the most popular methods to treat VOCs due to its environmental friendliness and simplicity of operation. Although a large number of reports have reviewed the application of catalytic oxidation for the degradation of VOCs, relatively few reports are based on this direction of metal organic frameworks (MOFs) and MOF derivatives. Herein, this paper reviews the recent applications of heterogeneous catalytic technologies in the degradation of VOCs, including photocatalysis, thermal catalysis and other catalytic approaches. The applications of MOFs and their derivatives in VOCs degradation, such as the progress of MOF-derived metal oxides in the treatment of toluene, were highlighted. The mechanisms of VOCs degradation by different catalytic approaches were systematically presented. Finally, we presented the views and directions of VOCs treatment technology development. We hope that this reaction type-oriented review will provide important insights into MOFs and MOF-derived materials for VOCs pollution control.

Defined metal atom aggregates precisely incorporated into metal-organic frameworks

Nanosized metal aggregates (MAs), including metal nanoparticles (NPs) and nanoclusters (NCs), are often the active species in numerous applications. In order to maintain the active form of MAs in "use", they need to be anchored and stabilised, preventing agglomeration. In this context, metal-organic frameworks (MOFs), which exhibit a unique combination of properties, are of particular interest as a tunable and porous matrix to host MAs. A high degree of control in the synthesis towards atom-efficient and application-oriented MA@MOF composites is required to derive specific structure-property relationships and in turn to enable design of functions on the molecular level. Due to the versatility of MA@MOF (derived) materials, their applications are not limited to the obvious field of catalysis, but increasingly include 'out of the box' applications, for example medical diagnostics and theranostics, as well as specialised (bio-)sensoring techniques. This review focuses on recent advances in the controlled synthesis of MA@MOF materials en route to atom-precise MAs. The main synthetic strategies, namely 'ship-in-bottle', 'bottle-around-ship', and approaches to achieve novel hierarchical MA@MOF structures are highlighted and discussed while identifying their potential as well as their limitations. Hereby, an overview of standard characterisation methods that enable a systematic analysis procedure and state-of-art techniques that localise MA within MOF cavities are provided. While the perspectives of MA@MOF materials in general have been reviewed various times in the recent past, few atom-precise MAs inside MOFs have been reported so far, opening opportunities for future investigation.

A new 2D layered aluminophosphate |Hada|6[Al6(PO4)8](H2O)11 supported highly uniform Ag nanoparticles for 4-nitrophenol reduction

This work presents a new 2D aluminophosphate (ZHKU-1) with inorganic sheets containing a 4,6,12-net in AAAA-stacked sequence. Moreover, small Ag clusters supported on ZHKU-1 exhibit excellent catalytic performance in 4-nitrophenol reduction.

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH₃) and temperature-programmed reduction (TPR-H₂) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

Transition Metal Oxodiperoxo Complex Modified Metal-Organic Frameworks as Catalysts for the Selective Oxidation of Cyclohexane

In this work, a series of modified metal-organic frameworks (MOFs) have been prepared by pre- and post-treatment with transition metal oxodiperoxo complexes (MoO(O₂)₂, WO(O₂)₂, and KVO(O₂)₂). The obtained materials are characterized by XRD, FTIR, SEM, TEM, inductively coupled plasma atomic emission spectrometry (ICP-AES), and X-ray photoelectron spectroscopy (XPS), as well as by N₂ adsorption/desorption measurement. The characterization results show that transition metal oxodiperoxo complexes are uniformly incorporated into the MOF materials without changing the basic structures. The performance of cyclohexane oxidation on metal oxodiperoxo complex modified MOFs are evaluated. UiO-67-KVO(O₂)₂ shows the best performance for cyclohexane oxidation, with 78% selectivity to KA oil (KA oil refers to a cyclohexanol and cyclohexanone mixture) at 9.4% conversion. The KA selectivity is found to depend on reaction time, while hot-filtration experiments indicates that the catalytic process is heterogeneous with no leaching of metal species.

One-Step Construction of Hydrophobic MOFs@COFs Core-Shell Composites for Heterogeneous Selective Catalysis

The exploration of novel porous core-shell materials is of great significance because of their prospectively improved performance and extensive applications in separation, energy conversion, and catalysis. Here, mesoporous metal-organic frameworks (MOFs) NH2-MIL-101(Fe) as a core generate a shell with mesoporous covalent organic frameworks (COFs) NUT-COF-1(NTU) by a covalent linking process, the composite NH2-MIL-101(Fe)@NTU keeping retentive crystallinity with hierarchical porosity well. Importantly, the NH2-MIL-101(Fe)@NTU composite shows significantly enhanced catalytic conversion and selectivity during styrene oxidation. It is mainly due to the hydrophilic MOF nanocrystals readily gathering the hydrophobic reactants styrene and boosting the radical mechanism path after combining the hydrophobic COFs shell. The synthetic strategy in this systematic study develops a new rational design for the synthesis of other core-shell MOF/COF-based hybrid materials, which can expand the promising applications.