Fabrication of MIL-53(Al)/Ag/AgCl plasmonic nanocomposite: An improved metal organic framework based photocatalyst for degradation of some organic pollutants

Recent Advances in Metal-Organic Framework (MOF)-Based Composites for Organic Effluent Remediation

Environmental pollution caused by organic effluents emitted by industry has become a worldwide issue and poses a serious threat to the public and the ecosystem. Metal-organic frameworks (MOFs), comprising metal-containing clusters and organic bridging ligands, are porous and crystalline materials, possessing fascinating shape and size-dependent properties such as high surface area, abundant active sites, well-defined crystal morphologies, and huge potential for surface functionalization. To date, numerous well designated MOFs have emerged as critical functional materials to solve the growing challenges associated with water environmental issues. Here we present the recent progress of MOF-based materials and their applications in the treatment of organic effluents. Firstly, several traditional and emerging synthesis strategies for MOF composites are introduced. Then, the structural and functional regulations of MOF composites are presented and analyzed. Finally, typical applications of MOF-based materials in treating organic effluents, including chemical, pharmaceutical, textile, and agricultural wastewaters are summarized. Overall, this review is anticipated to tailor design and regulation of MOF-based functional materials for boosting the performance of organic effluent remediation.

Microwave-assisted MOF@biomass layered nanomaterials: Characterization and applications in wastewater treatment

MOF@Biomass layered hybrids were designed through in situ growth from rice husk (RH) and microwave-assisted synthesized MIL-53(Al) particles that enable the reduction of reaction times. The synthesis process included steps to pretreat RH, Al adsorption on RH, and then MIL-53(Al) in-situ growth reaction at 125 °C for 60 min and 200 W irradiation power. The resulting hybrid (MIL-53(Al)@RH) and its parent separate materials were characterized using TGA, SEM, FTIR, XRD, among others. MIL-53(Al)@RH showed high crystallinity in the hybridized MOF particles, thermal decomposition phases, and functional groups (Al-O, O-H, CO, and CC). The hybrid particles allow an easy separation during heterogeneous processing due to their 400 times larger size compared to MIL-53(Al) crystals. The properties of the layered hybrids for removal of Oxytetracycline (OTC), Diclofenac (DCL), and Glyphosate (GLY) in aqueous solutions, were tested by adsorption (ADS) and advanced oxidation processes (AOP). The high ADS capacities (162 mg g^-1 GLY, 139 mg g^-1 OTC, 93 mg g^-1 DCL) and % removal in AOP (97% GLY, 91% OTC, 80% DCL) demonstrated that MIL-53(Al) maintained its properties after hybridization.

Graphdiyne (CnH2n-2)-Based GDY/CuI/MIL-53(Al) S-Scheme Heterojunction for Efficient Hydrogen Evolution

Graphdiyne (g-C_nH_2n-2) is a new carbon material composed of sp and sp² hybrid carbon atoms. Since the synthesis by Li's team, graphdiyne has been widely studied in other fields because of its excellent properties. In this paper, graphdiyne was synthesized from copper-containing materials and the composite GDY/CuI/MIL-53(Al) S-scheme heterojunction is prepared for photocatalytic cracking of water to produce hydrogen. First, GDY/CuI was prepared by organic synthesis, and then GDY/CuI was anchored on the surface of MIL-53(Al) by in situ ultrasonic stirring. After the continuous optimization of experimental conditions, the final hydrogen evolution rate is much higher than that of MIL-53(Al). This efficient photocatalytic performance can be attributed to the S-scheme heterojunction formed by the unique energy band arrangement. At the same time, the mechanism of charge transfer was demonstrated by in situ irradiation X-ray photoelectron spectroscopy. The strong interaction among the three strongly promotes the separation and transfer of photogenerated electron-hole pairs.

Conductive Aramid Fibers from Electroless Silver Plating of Crosslinked HPAMAM-Modified PPTA: Preparation and Properties

Conductive aramid (PPTA) fibers are highly needed for making flexible conductive materials, antistatic materials, and electromagnetic shielding materials. In this work, silver-plated conductive PPTA fibers with high conductivity and excellent mechanical properties were prepared by the electroless plating of PPTA fibers modified with crosslinked hyperbranched polyamide-amine (HPAMAM). The crosslinked HPAMAM creates a stable interface between the PPTA fibers and the silver plating. The morphology and physicochemical properties of the modified and the silver-plated fibers were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Three epoxy crosslinking agents with different chain lengths were used to crosslink HPAMAM, and the effects of HPAMAM concentration, crosslinking agent dosage, and crosslinking time on the resistance of the fibers were studied. The long chain crosslinking agent appears to be beneficial to silver plating. The lowest resistance (0.067 Ω/cm) was attained when HPAMAM was modified by diethylene glycol diglycidyl ether (1:1 molar ratio), and 20 g/L HPAMAM was used to modify the PPTA fibers. The tensile strength of the original PPTA fibers decreased by only 3% or less after silver plating.

Recent advances in the tuning of the organic framework materials - The selections of ligands, reaction conditions, and post-synthesis approaches

Organic framework materials, particularly metal-organic frameworks (MOFs), graphene-organic frameworks (GOFs), and covalent organic frameworks (COFs), have led to the revolution across fields including catalysts, sensors, gas capture, and biology mainly owing to their ultra-high surface area-to-volume ratio, on-demand tunable crystal structures, and unique surface properties. While the wet chemistry routes have been the predominant synthesis approach, the crystal phase, morphological parameters, and physicochemical properties of organic framework materials are largely affected by various synthesis parameters and precursors. In this work, we specifically review the influences of synthesis parameters towards crystal structures and chemical compositions of organic framework materials, including selected ligand types and lengths, reaction temperature/solvent/reactant compositions, as well as post-synthesis modification approaches. More importantly, the subsequent impacts on the general electronic, mechanical, surface chemical, and thermal properties as well as the consequent variation in performances towards catalytic, desalination, gas sensing, and gas storage applications are critically discussed. Finally, the current challenges and prospects of organic framework materials are provided.

One-step fabrication of novel MIL-53(Fe, Al) for synergistic adsorption-photocatalytic degradation of tetracycline

Bimetallic MOFs (MIL-53 (Fe, Al)) were successfully fabricated via a facile one-step solvothermal method for the removal of tetracycline (TC) from aqueous solutions. Tetracycline adsorption and photocatalytic experiments indicate that the optimum bimetallic synthetic molar ratio is 3:2 (40%MIL-53(Fe, Al)). The adsorption data are well fitted by the Freundlich model and pseudo-second-order adsorption kinetics. 40%MIL-53(Fe, Al) has an adsorption capacity of up to 402.033 mg/g. After the dark adsorption phase, 10 mg of 40%MIL-53(Fe, Al) can remove 94.33% of the tetracycline in a 70 mL aqueous solution (20 mg/L) under 50 min irradiation, while only 71.39% and 81.82% of the tetracycline are removed by MIL-53(Fe) and MIL-53(Al) under the same conditions. In addition, 40%MIL-53(Fe, Al) exhibits a significant adsorption-photocatalytic synergy (under direct irradiation without a dark adsorption phase), in which the pseudo-first-order kinetic constant increases by a factor of 3.11. Quenching experiments and ESR characterization indicate that ·O₂^-, ·OH, and h⁺ are the main active species in the photocatalytic process. Meanwhile, 40%MIL-53(Fe, Al) demonstrates good stability, with a tetracycline removal rate that still reaches 83.70% after 4 cycles. These results suggest that the prepared 40%MIL-53(Fe, Al) catalyst is a novel adsorption-photocatalytic material that can be used for the efficient treatment of tetracycline.

GNP/Al-MOF nanocomposite as an efficient fiber coating of headspace solid-phase micro-extraction for the determination of organophosphorus pesticides in food samples

The synthesis and utilization of a high porous nanocomposite comprising MIL-53(Al) metal-organic framework (Al-MOF) and graphene nanopowder (GNP) is reported as a fiber coating for headspace solid-phase micro-extraction (HS-SPME) of selected organophosphorus pesticides (OPPs) from apple, potato, grape juice, tomato, and river water. The adsorbed OPPs on the coated fiber were subsequently determined using GC-MS. Several parameters affecting the efficiency of extraction including time and temperature of extraction, desorption condition of extracted analytes, pH and agitation of sample solution, and salt concentration were investigated. The optimum extraction condition was achieved at 70 °C with an extraction time of 40 min, pH = 4-8, and NaCl concentration of 6.0% (w/v). The best condition of desorption were observed at 280 °C for 2.0 min under a flow of helium gas in the GC inlet. Under optimal conditions, the detection limits ranged from 0.2 to 1.5 ng g^-1 and the linear ranges between 0.8 and 600 ng g^-1. The proposed method showed very good repeatability with RSD values ranging from 4.5 to 7.3% (n = 5). The relative recoveries were between 88% and 109% at the spiked level of 25.0 ng g^-1 for the tomato sample. The fabricated fiber exhibited good enrichment factor (62-195) at optimum condition of HS-SPME. The applied HS-SPME technique is facile, fast, and inexpensive. The thermally stable GNP/Al-MOF exhibited a high sensitivity toward OPPs. So, this nanocomposite can be considered as a sorbent for the micro-extraction of other pesticides in food.

Investigation of five metal organic frameworks as sorbent in syringe filters-SPE method for determination of metronidazole and cephalexin in water samples

In this study, we evaluated the preparation and utilization of NH2-MIL-101(Al) and NH2-MIL-101(Cr) as two efficient adsorbents for extraction of metronidazole and cephalexin in water samples using syringe filters-SPE method....

Development of a SPE/GC-MS method for the determination of organophosphorus pesticides in food samples using syringe filters packed by GNP/MIL-101(Cr) nanocomposite

In this study, we report the synthesis and application of a nanocomposite comprising metal-organic framework MIL-101(Cr) and graphene nanopowder (GNP) as a promising sorbent for the extraction of organophosphorus pesticides (OPPs) in juices, water, vegetables and honey samples. A syringe filter, for the first time, was used to host the synthesized nanocomposite and extract the OPPs followed by GC-MS analysis. Different characterization methods including XRD, FTIR, TGA, BET and SEM were employed to confirm the formation of studied nanocomposite. The results indicated that the GNP/MIL-101(Cr) could provide higher capacity for adsorption of OPPs and lower detection limit compared to pristine MIL-101(Cr). The detection limits were 0.005 to 15.0 µg/Kg and the linear range found between 0.05 and 400 µg/Kg. The proposed method showed very good repeatability with the RSD values ranging from 2.9% to 7.1%. The recoveries were between 84% -110% with the spiked levels of 2.0-100.0 µg/Kg.

MIL-53 Metal-Organic Framework as a Flexible Cathode for Lithium-Oxygen Batteries

Li-air batteries possess higher specific energies than the current Li-ion batteries. Major drawbacks of the air cathode include the sluggish kinetics of the oxygen reduction (OER), high overpotentials and pore clogging during discharge processes. Metal-Organic Frameworks (MOFs) appear as promising materials because of their high surface areas, tailorable pore sizes and catalytic centers. In this work, we propose to use, for the first time, aluminum terephthalate (well known as MIL-53) as a flexible air cathode for Li-O₂ batteries. This compound was synthetized through hydrothermal and microwave-assisted routes, leading to different particle sizes with different aspect ratios. The electrochemical properties of both materials seem to be equivalent. Several behaviors are observed depending on the initial value of the first discharge capacity. When the first discharge capacity is higher, no OER occurs, leading to a fast decrease in the capacity during cycling. The nature and the morphology of the discharge products are investigated using ex situ analysis (XRD, SEM and XPS). For both MIL-53 materials, lithium peroxide Li₂O₂ is found as the main discharge product. A morphological evolution of the Li₂O₂ particles occurs upon cycling (stacked thin plates, toroids or pseudo-spheres).