Highly efficient capture of benzothiophene with a novel water-resistant-bimetallic Cu-ZIF-8 material

Innovations in metal-organic frameworks (MOFs): Pioneering adsorption approaches for persistent organic pollutant (POP) removal

Adsorption is a promising way to remove persistent organic pollutants (POPs), a major environmental issue. With their high porosity and vast surface areas, MOFs are suited for POP removal due to their excellent adsorption capabilities. This review addresses the intricate principles of MOF-mediated adsorption and helps to future attempts to mitigate organic water pollution. This review examines the complicated concepts of MOF-mediated adsorption, including MOF synthesis methodologies, adsorption mechanisms, and material tunability and adaptability. MOFs' ability to adsorb POPs via electrostatic forces, acid-base interactions, hydrogen bonds, and pi-pi interactions is elaborated. This review demonstrates its versatility in eliminating many types of contaminants. Functionalizing, adding metal nanoparticles, or changing MOFs after they are created can improve their performance and remove contaminants. This paper also discusses MOF-based pollutant removal issues and future prospects, including adsorption capacity, selectivity, scale-up for practical application, stability, and recovery. These obstacles can be overcome by rationally designing MOFs, developing composite materials, and improving material production and characterization. Overall, MOF technology research and innovation hold considerable promise for environmental pollution solutions and sustainable remediation. Desorption and regeneration in MOFs are also included in the review, along with methods for improving pollutant removal efficiency and sustainability. Case studies of effective MOF regeneration and scaling up for practical deployment are discussed, along with future ideas for addressing these hurdles.

Diatomite supported highly-dispersed ZnO/Zn-co-embedded ZIF-8 derived porous carbon composites for adsorption desulfurization

The metal organic framework (MOFs)-derived porous carbon materials with highly dispersed metal active sites were of the exclusive application foreground in many field, such as catalyst, electrochemistry, adsorption desulfurization and so on. However, the loss issue of metal active sites in MOFs frame was indispensable during the high temperature carbonization because of the lower boiling point of many metals, thus fundamentally affecting the atom-scale uniform distribution merit of MOFs-derived porous carbon materials. This work was to provide a novel strategy to address the loss issue of the active metal volatilization in the fabrication of MOFs-derived porous carbon materials. The ZnO nanosheets were pre-grown on the surface of diatomite by using in-situ microwave-assisted preparation, and thereafter the Zn-containing ZIF-8 particles covered the surface of ZnO nanosheets by virtue of the ZnO-induced growth. The results affirmed that the high content Zn-doped porous carbon materials were achieved and the Zn volatilization in MOFs was restrained on account of the occurrence of ZnO on diatomite (DE) surface during the carbonization. The adsorption desulfurization performance of the ZnO/Zn-embedded porous carbon materials/DE (ZnO/Zn/C@DE) was examined by the sulfur-containing compounds in simulated oil. The adsorption desulfurization performance investigation indicated that the ZnO/Zn/C@DE had the optimum adsorption capacities of 45.3 mg/g for benzothiophene and 37.4 mg/g for thiophene. Nonetheless, the competitive adsorption desulfurization finding of toluene in simulated oil showed that the adsorption capacities of ZnO/Zn/C@DE for TH and BT were dramatically descended, suggesting the presence of S-M interaction, wherein S stood for the S atom in a thiophene molecule and their analogs, and M for Zn atoms in porous carbon materials.

Defective copper-based metal-organic frameworks for the efficient extraction of organosulfur compounds from garlic-processing wastewater

Organosulfur compounds (OSCs) in garlic-processing wastewater are decomposed and generated to toxic and harmful substances with unpleasant odors under anaerobic conditions. Herein, were report the successful development of novel copper-based metal organic framework (Cu-MOF) adsorbents with high adsorption capacities for OSCs in aqueous media. Defect-rich Cu-MOF-X samples, with particle sizes between 360 and 750 nm, synthesized hydrothermal in the presence of acetic acid (where X denotes the molar ratio of acetic acid relative to the pentadentate MOF linker H4PPYD). OSC adsorption experiments using allicin, ajoene and 2-ethenyl-4H-1,3-dithiine (2-VDT) showed that Cu-MOF-200 delivered fast adsorption kinetics and high OSC adsorption capacities (149.02-171.33 mg g-1) owing to the pore accessibility and range of adsorption sites in the MOF. FT-IR, Raman, and XPS analyses, together with density functional theory (DFT) calculations, verified the strong yet reversible adsorption of OSCs in Cu-MOF-200. Results guide the development of improved adsorbents for OSC capture from garlic-processing wastewater.

Bimetal doped Cu-Fe-ZIF-8/g-C3N4 nanocomposites for the adsorption of tetracycline hydrochloride from water

Bimetal doped Cu-Fe-zeolitic imidazole framework-8 (ZIF-8)/graphitic carbon nitride (GCN) (Cu-Fe-ZIF-8/GCN) nanocomposites were prepared via one-pot and ion-exchange methods. The main influencing factors, such as adsorbent concentration, TC concentration, initial pH, and coexisting ions, were evaluated in detail. Due to the suitable pore structures and the presence of multiple interactions on the surface, the nanocomposite showed a high adsorption capacity up to 932 mg g-1 for tetracycline hydrochloride (TC), outperforming ZIF-8 by 4.8 times. The adsorption kinetics and adsorption isotherm were depicted in good detail using pseudo-second-order kinetic and Langmuir models, respectively. Thermodynamic calculation revealed that the adsorption of the nanocomposite under experimental conditions was a spontaneous heat absorption process, and was primarily driven by chemisorption. After four cycles of use, the nanocomposite retained 87.2% of its initial adsorption capacity, confirming its high reusability and broad application prospects in removing tetracycline-type pollutants from wastewater.

One-Pot Rapid Synthesis of Cu2+-Doped GOD@MOF to Amplify the Antitumor Efficacy of Chemodynamic Therapy

Chemodynamic therapy (CDT) relies on the transformation of intracellular hydrogen peroxide (H₂O₂) to hydroxyl radicals (·OH) with higher toxicity under the catalysis of Fenton/Fenton-like reagents, which amplifies the oxidative stress and induces significant cellular apoptosis. However, the CDT efficacy is generally limited by the overexpressed GSH and insufficient endogenous H₂O₂ in tumors. Co-delivery of Cu²⁺ and glucose oxidase (GOD) can lead to a Cu²⁺/Cu⁺ circulation to realize GSH depletion and amplify the Fenton-like reaction. pH-responsive metal-organic frameworks (MOFs) are the optical choice to deliver Fenton/Fenton-like ions to tumors. However, considering that the aqueous condition is requisite for GOD encapsulation, it is challenging to abundantly dope Cu²⁺ in ZIF-8 MOF nanoparticles in aqueous conditions due to the ease of precipitation and enlarged crystal size. In this work, a robust one-pot biomimetic mineralization method using excessive ligand precursors in aqueous conditions is developed to synthesize GOD@Cu-ZIF-8. Copper ions abundantly doped to the GOD@Cu-ZIF-8 can eliminate GSH to produce Cu⁺, which is further proceeded to the Fenton-like reaction in the presence of GOD-catalyzed H₂O₂. Through breaking the tumor microenvironment homeostasis and producing an enhanced CDT effect, the promising antitumor capability of GOD@Cu-ZIF-8 was evidenced by the experiments both in vitro and in vivo.

Encapsulated laccase in bimetallic Cu/Zn ZIFs as stable and reusable biocatalyst for decolorization of dye wastewater

Laccase have received extensive attention in pollutant degradation, but its practical viability is largely affected by the poor stability, easy inactivation and difficulty in recycling for the present. Enzyme immobilization offers enhanced enzyme stability and constructs a synergistic system for the efficient adsorption and degradation of pollutants. In this study, bimetallic Cu/Zn ZIFs were synthesized by co-precipitation method as the protective carrier for laccase. Lac@Cu-ZIF-90 exhibited a good protective effect on laccase and showed a high operational stability in various interfering environments. Free laccase was completely inactivated at pH 7.0 but Lac@Cu-ZIF-90 could maintain 50.0 % activity. Benefiting from the encapsulation of laccase and porous structure of Cu-ZIF-90, the Lac@Cu-ZIF-90 exhibited decolorization efficiency for dye wastewater. More importantly, the Lac@Cu-ZIF-90 could be recovered from the dye solution and re-used to adsorb and degrade the synthetic dye for multiple times, its removal rate for reactive deep green was only decreased about 10.8 % after five cycles. This work reveals that the Cu-ZIF-90 provides a favorable environment for laccase and as a protective layer to relieve the conformation change, which provides an efficient strategy to decolorize dye wastewater. Therefore, Cu-ZIF-90 promises applications as enzymes encapsulation has great potential in water remediation.

Well-constructed approach of exceptionally water-stable (mesoporous SiO2)-on-(microporous Cu-BTC) composite for efficient methylene blue capture

A novel (mesoporous SiO2)-on-(microporous Cu-BTC) exhibits good hydrothermal stability and methylene blue capture ability.

Bimetallic Co/Zn zeolitic imidazolate framework ZIF-67 supported Cu nanoparticles: An excellent catalyst for reduction of synthetic dyes and nitroarenes

In this study, a sub-class of microporous crystalline metal organic frameworks (MOFs) with zeolite-like configurations, i.e., zeolitic imidazolate frameworks of single node ZIF-67 and binary nodes ZIF-Co/Zn are used as the supports to develop Cu nanoparticles based nanocatalysts. Their catalytic activities are comparatively evaluated where Cu(x)@ZIF-Co/Zn exhibits better performances than Cu(x)@ZIF-67 in the reduction of synthetic dyes and nitroarenes. For instance, the Cu(0.25)@ZIF-Co/Zn catalyst shows an excellent reaction rate of 2.088 × 10^-2 s^-1 and an outstanding activity of 104.4 s^-1g_cat^-1 for the reduction of methyl orange. The same catalyst also performs an exceptional catalytic activity in the hydrogenation of p-nitrophenol to p-aminophenol with the activity of 216.5 s^-1g_cat^-1. A synergistic role of unique electronic properties rising from the direct contact of Cu NPs with the bimetallic nodes ZIF-Co/Zn, higher surface area of support, appropriate Cu loading and maintainable microporous frameworks with higher thermal and hydrolytic stability collectively enhances the catalytic activity of Cu(x)@ZIF-Co/Zn. Moreover, this catalyst shows excellent stability and recyclability, which can retain high conversion after reuse for 10 cycles.

Mixed-Metal Cu-BTC Metal-Organic Frameworks as a Strong Adsorbent for Molecular Hydrogen at Low Temperatures

The advancement of hydrogen and fuel cell technologies hinges on the development of hydrogen storage methods. Metal-organic frameworks (MOFs) are one of the most favorable materials for hydrogen storage. In this study, we synthesized a series of isostructural mixed-metal metal-organic frameworks (MM-MOFs) of 1,3,5-benzenetricarboxylate (BTC), M-Cu-BTC, where M = Zn²⁺, Ni²⁺, Co²⁺, and Fe²⁺ using the post-synthetic exchange (PSE) method with metal ions. The powder X-ray diffraction patterns of MM-MOFs were similar with those of single-metal Cu-BTC. Scanning electron microscopy indicates the absence of amorphous phases. Inductively coupled plasma mass spectroscopy of the MM-MOFs shows successful metal exchanges using the PSE method. The N₂ adsorption measurements confirmed the successful synthesis of porous MM-MOFs. The metal exchanged materials Ni-Cu-BTC, Zn-Cu-BTC, Fe-Cu-BTC, and Co-Cu-BTC were studied for hydrogen storage and showed a gravimetric uptake of 1.6, 1.63, 1.63, and 1.12 wt %; respectively. The increase in hydrogen adsorption capacity for the three metal exchanged materials is about 60% relative to that of the parent MOF (Cu-BTC). The improvement of gravimetric uptake in M-Cu-BTC (where M = Ni²⁺, Zn²⁺, and Fe²⁺) is probably due to the increase in binding enthalpy of H₂ with the unsaturated metal sites after the partial exchange from Cu²⁺ to other metal ions. The higher charge density of metal ions strongly polarizes hydrogen and provides the primary binding sites inside the pores of Cu-BTC and subsequently enhances the gravimetric uptake of hydrogen.

Reusable, few-layered-MoS2 nanosheets/graphene hybrid on cellulose paper for superior adsorption of methylene blue dye

High efficient methylene blue adsorption by MoS₂ micro-flowers on graphene-cellulose paper.