Ultrasonic-assisted synthesis of nano-sized metal-organic framework; a simple method to explore selective and fast Congo Red adsorption

The influence of HKUST-1 and MOF-76 hand grinding/mechanical activation on stability, particle size, textural properties and carbon dioxide sorption

In this study, we explore the mechanical treatment of two metal-organic frameworks (MOFs), HKUST-1 and MOF-76, applying various milling methods to assess their impact on stability, porosity, and CO2 adsorption capacity. The effects of different mechanical grinding techniques, such as high-energy ball milling and hand grinding, on these MOFs were compared. The impact of milling time, milling speed and ball size during high-energy ball milling was assessed via the Design of Experiments methodology, namely using a 33 Taguchi orthogonal array. The results highlight a marked improvement in CO2 adsorption capacity for HKUST-1 through hand milling, increasing from an initial 25.70 wt.% (5.84 mmol g-1) to 41.37 wt.% (9.40 mmol g-1), marking a significant 38% increase. In contrast, high-energy ball milling seems to worsen this property, diminishing the CO2 adsorption abilities of the materials. Notably, MOF-76 shows resistance to hand grinding, closely resembling the original sample's performance. Hand grinding also proved to be well reproducible. These findings clarify the complex effects of mechanical milling on MOF materials, emphasising the necessity of choosing the proper processing techniques to enhance their stability, texture, and performance in CO2 capture and storage applications.

Recent advances in metal-organic frameworks: Synthesis, application and toxicity

Metal-organic frameworks (MOFs) are a new class of crystalline porous hybrid materials with high porosity, large specific surface area and adjustable channel structure and biocompatibility, which are being investigated with increasing interest for energy storage and conversion, gas adsorption/separation, catalysis, sensing and biomedicine. However, the practical applications of MOFs make them release into the environment inevitable, posing a threat to humans and organisms. In this article, we cover advances in the currently available MOFs synthesis methods and the emerging applications of MOFs, especially in the biomedical field (therapeutic agents and bioimaging). Additionally, after evaluating the current status of main exposure routes and affecting factors in the field of MOFs-toxicity, the molecular mechanism is also clarified and identified. Knowledge gaps are identified from such a summarization and frontier development are explored for MOFs. Afterwards, we also present the limitations, challenges, and future perspectives in the study of the entire life cycle of MOFs. This review emphasizes the need for a more targeted discussion of the latest, widely used and effective versatile material class in order to exploit the full potential of high-performance and non-toxicity MOFs in the future.

An Anionic Porous Indium-Organic Framework with Nitrogen-Rich Linker for Efficient and Selective Removal of Trace Cationic Dyes

Metal-organic frameworks (MOFs) with porosity and functional adjustability have great potential for the removal of organic dyes in the wastewater. Herein, an anionic porous metal-organic framework (MOFs) [Me₂NH₂]₂In₂[(TATAB)₄(DMF)₄]·(DMF)₄(H₂O)₄ (HDU-1) was synthesized, which is constructed from a [In(OOC)₄]^- cluster and a nitrogen-rich linker H₃TATAB (4,4',4″-s-triazine-1,3,5-triyltri-p-aminobenzoic acid). The negatively charged [In(OOC)₄]^- cluster and uncoordinated -COOH on the linker result in one unit cell of HDU-1 having 8 negative sites. The zeta potential of -20.8 mV dispersed in pure water also shows that HDU-1 possesses negatively charged surface potential. The high electronegativity, water stability, and porosity of HDU-1 can facilitate the ion-exchange and Coulombic interaction. As expected, the HDU-1 exhibits high selectivity and removal rates towards trace cationic dyes with suitable size, such as methylene blue (MB) (96%), Brilliant green (BG) (99.3%), and Victoria blue B (VB) (93.6%).

Adsorption efficacy of functionalized Cu-BDC MOFs tethered 2-mercaptobenzimidazole analogue: A comparative study

A novel metal-organic framework [MOFs], and 2-[benzo [d]thiazol-2-ylthio)-3-hydroxy acrylaldehyde-Cu-benzene dicarboxylic acid was synthesized by solvothermal method and characterized using p-XRD, FSEM-EDX, TGA, BET, FTIR. The tethered organic linker, 2-[benzo [d]thiazol-2-ylthio)-3-hydroxyacrylaldehyde was commonly known as 2-mercaptobenimidazole analogue [2-MBIA]. Analysis of BET disclosed that addition of 2-MBIA to Cu-benzene dicarboxylic acid [Cu-BDC], reduced the crystallite size from 70.0 nm to 65.90 nm, surface area from 17.95 to 17.02 m² g^-1 and enhances the pore size from 5.84 nm with 0.027 cm³ g^-1 pore volume to 8.74 nm with 0.361 cm³ g^-1 pore volume. Batch experiments were conducted to optimize pH, adsorbent dosage, and, Congo red (CR) concentration. The adsorption percentage of CR on the novel MOFs was 54%. Adsorption kinetic studies revealed that the uptake adsorption capacity at equilibrium was 184.7 mg/g from pseudo-first-order kinetics which gave a good fit with the experimental data. Intraparticle diffusion model explained the process of the adsorption mechanism: diffusion from the bulk solution onto the porous surface of the adsorbent. Freundlich and Sips models were the best fit models of the several non-linear isotherm models. Temkin isotherm suggested the adsorption of CR on MOFs was of an exothermic nature.

A novel carbonized derivative of Fe-Cu bimetallic organic framework (Fe-Cu-MOF@C): preparation and optimization

A carbon derivative with Fe-Cu bimetallic organic framework (Fe-Cu-MOF@C) was prepared by microwave synthesis and pyrolysis. Using potassium persulfate (PS) as oxidant and 2,4-dichlorophenol (2,4-DCP) as target pollutant, the optimal preparation conditions of Fe-Cu-MOF@C were studied. The factors affecting the synthesis of Fe-Cu-MOF include microwave power, microwave time, microwave temperature, the molar ratio of metal ions to organic ligands, the molar ratio of iron and copper, etc. In addition, the influence of pyrolysis temperature on the performance of Fe-Cu-MOF@C cannot be ignored. The results show that Fe-Cu-MOF@C has the best catalytic performance when the microwave time is 30 min, the microwave power is 600 W, the microwave temperature is 150 °C, the molar ratio of (Fe²⁺ + Cu²⁺)/H₂BDC is 10:3, the molar ratio of Fe²⁺/Cu²⁺ is 10:1, and the pyrolysis temperature is 700 °C. After 90 min of reaction, 2,4-DCP was completely removed. Repeatable experiments show that Fe-Cu-MOF@C has good stability and its service life can be restored by heat treatment. In this study, a heterogeneous catalyst with strong catalytic capacity, high stability and easy recovery was prepared by a simple and efficient process, which is conducive to the development of advanced oxidation technology and the progress of water environmental protection.

Ultrasonically synthesized MOFs for modification of polymeric membranes: A critical review

Metal-organic framework (MOF) membranes hold the promise for energy-efficient separation processes. These nanocrystalline compounds can effectively separate materials with different sizes and shapes at a molecular level. Furthermore, MOFs are excellent candidates for improving membrane permeability and/or selectivity due to their unique properties, such as high specific area and special wettability. Generally, MOFs can be used as fillers in mixed matrix membranes (MMMs) or incorporated onto the membrane surface to modify the top layer. Characteristics of the MOFs, and correspondingly, the properties of the MOF-based membranes, are majorly affected by their production technique. This critical review discusses the sonication technique for MOF production and the opportunities and challenges of using MOF for making membranes. Effective parameters on the characteristics of the synthesized MOFs, such as sonication time and power, were discussed in detail. Although the ultrasonically synthesized MOFs have shown great potential in the fabrication/modification of membranes for gas and liquid separation/purification, so far, no comprehensive and critical review has been published to clarify such accomplishments and technological gaps for the future research direction. This paper aims to review the most recent research conducted on ultrasonically synthesized MOF for the modification of polymeric membranes. Recommendations are provided with the intent of identifying the potential future works to explore the influential sonication parameters.

Shape- and size-dependent desorption kinetics and surface acidity of nano-SnO2

With the decrease of particle size, Ed and ln A increase, and Ed octahedron > Ed sphere and ln A octahedron > ln A sphere.

Acyl amide-functionalized and water-stable iron-based MOF for rapid and selective dye removal

Acyl amide-functionalized, highly porous and water-stable Fe3O cluster-based MOF for rapid and selective organic dye adsorption.

Solvent-tuned ultrasonic synthesis of 2D coordination polymer nanostructures and flakes

Herein, a new 2-dimensional coordination polymer based on copper (II), {Cu2(L)(DMF)2}n, where L stands for 1,2,4,5-benzenetetracarboxylate (complex 1) is synthesized. Interestingly, we demonstrate that both solvent and sonication are relevant in the top-down fabrication of nanostructures. Water molecules are intercalated in suspended crystals of complex 1 modifying not only the coordination sphere of Cu(II) ions but also the final chemical formula and crystalline structure obtaining {[Cu(L)(H2O)3]·H2O}n (complex 2). On the other hand, ultrasound is required to induce the nanostructuration. Remarkably, different morphologies are obtained using different solvents and interconversion from one morphology to another seems to occur upon solvent exchange. Both complexes 1 and 2, as well as the corresponding nanostructures, have been fully characterized by different means such as infrared spectroscopy, x-ray diffraction and microscopy.

Ultrasound-irradiated synthesis of 3-mercaptopropyl trimethoxysilane-modified hydroxyapatite derived from fish-scale residues followed by ultrasound-assisted organic dyes removal

We report a novel method for the synthesis of 3-mercaptopropyl trimethoxysilane-modified hydroxyapatite (FHAP-SH) derived from fish-scale residues by using ultrasound irradiation. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used for the FHAP-SH characterization. Then, the organic dye adsorption on the FHAP-SH was monitored through an ultrasound process. After the dye removal optimization, significant improvements were observed in the maximum adsorption capacities for Congo Red (CR, 500 mg g^-1), Coomassie Brilliant Blue G 250 (CB, 235 mg g^-1), and Malachite Green (MG, 625 mg g^-1). The adsorption behaviors of these dyes were fitted by using the Langmuir isotherm model with a high coefficient of determination values ranging from 0.9985 to 0.9969. The adsorption of the three dyes onto FHAP-SH was an endothermic process based on the adsorption thermodynamics model, while the adsorption kinetics analysis of the dyes presented a good alignment with the pseudo-second-order kinetics. The FHAP-SH exhibits a remarkably high adsorption capacity, is inexpensive, and fulfills the ecofriendly requirements of dye wastewater treatment, especially in the textile industry.

Optimized Preparation of Nanosized Hollow SSZ-13 Molecular Sieves with Ultrasonic Assistance

Because of its unique eight-membered ring pore structure and the arrangement of cations in its structure, the SSZ-13 molecular sieve has a higher affinity for CO2 than other gases, meaning it has attracted more attention than other porous materials for CO2 adsorption. However, the expensive template and long preparation time limits the industrial production of SSZ-13. In this work, a hollow structure was successfully introduced into the nanosized SSZ-13 molecular sieve with ultrasonic treatment. The effects of the amount of seed added and the ultrasonic time on the structure were investigated. When the amount of seed added was 0.5 wt.% and the ultrasonic time was 60 min, the sample showed a hollow cubic crystal with a diameter of about 50 nm. The specific surface area reached 791.50 m2/g, and the mesoporous ratio was 66.3%. The samples were tested for CO2 adsorption performance at 298 K. It was found that the hollow sample prepared in this work has higher CO2 adsorption capacity compared with the SSZ-13 zeolite prepared with conventional methods. When the adsorption pressure was 0.27 bar, the adsorption amount reached 2.53 mmol/g. The hollow SSZ-13 molecular sieve reached a CO2 adsorption capacity of 4.24 mmol/g at 1 bar.