Atomically unveiling the structure-activity relationship of biomacromolecule-metal-organic frameworks symbiotic crystal.

Crystallization of biomacromolecules-metal-organic frameworks (BMOFs) allows for orderly assemble of symbiotic hybrids with desirable biological and chemical functions in one voxel. The structure-activity relationship of this symbiotic crystal, however, is still blurred. Here, we directly identify the atomic-level structure of BMOFs, using the integrated differential phase contrast-scanning transmission electron microscopy, cryo-electron microscopy and x-ray absorption fine structure techniques. We discover an obvious difference in the nanoarchitecture of BMOFs under different crystallization pathways that was previously not seen. In addition, we find the nanoarchitecture significantly affects the bioactivity of the BMOFs. This work gives an important insight into the structure-activity relationship of BMOFs synthesized in different scenarios, and may act as a guide to engineer next-generation materials with excellent biological and chemical functions.

UiO-66-NH2 and Zeolite-Templated Carbon Composites for the Degradation and Adsorption of Nerve Agents.

Composites of metal-organic frameworks and carbon materials have been suggested to be effective materials for the decomposition of chemical warfare agents. In this study, we synthesized UiO-66-NH2/zeolite-templated carbon (ZTC) composites for the adsorption and decomposition of the nerve agents sarin and soman. UiO-66-NH2/ZTC composites with good dispersion were prepared via a solvothermal method. Characterization studies showed that the composites had higher specific surface areas than pristine UiO-66-NH2, with broad pore size distributions centered at 1-2 nm. Owing to their porous nature, the UiO-66-NH2/ZTC composites could adsorb more water at 80% relative humidity. Among the UiO-66-NH2/ZTC composites, U0.8Z0.2 showed the best degradation performance. Characterization and gas adsorption studies revealed that beta-ZTC in U0.8Z0.2 provided additional adsorption and degradation sites for nerve agents. Among the investigated materials, including the pristine materials, U0.8Z0.2 also exhibited the best protection performance against the nerve agents. These results demonstrate that U0.8Z0.2 has the optimal composition for exploiting the degradation performance of pristine UiO-66-NH2 and the adsorption performance of pristine beta-ZTC.

Removal of organic contaminants from wastewater with GO/MOFs composites.

Graphene oxide/metal-organic frameworks (GO/MOFs) have been prepared via solvothermal synthesis with ferrous sulfate heptahydrate, zirconium acetate and terephthalic acid for the purpose of removing organic pollutants from wastewater. The composites were analyzed using scanning electron microscopy, infrared spectrometry, and XRD. Tetracycline hydrochloride and orange II were implemented as model pollutants to evaluate the efficacy of the GO/MOFs in water purification, in which 50 mg of Zr/Fe-MOFs/GO was mixed with 100 mL of 10 mg/L, 20 mg/L, 30 mg/L, or 50 mg/L tetracycline hydrochloride solution and 25 mg/L, 35 mg/L, 45 mg/L, or 60 mg/L orange II solution, respectively. The removal efficacy after 4 hours was determined to be 96.1%, 75.8%, 55.4%, and 30.1%, and 98.8%, 91.9%, 71.1%, and 66.2%, respectively. The kinetics of pollutant removal was investigated for both tetracycline hydrochloride and orange II and excellent correlation coefficients of greater than 0.99 were obtained. The high efficacy of these MOFs in pollutant removal, coupled with their inexpensive preparation indicates the feasibility of their implementation in strategies for treating waste liquid. As such, it is anticipated that Zr/Fe-MOFs/GO composites will be widely applied in wastewater purification.

Applications of zeolitic imidazolate framework-8 (ZIF-8) in bone tissue engineering: A review.

Bone tissue is a highly vascularized and dynamic tissue that continues to remodel throughout the life cycle of a person. Only a few researches are done on usage of zeolitic imidazolate framework-8 (ZIF-8) in the bone tissue engineering area. Hence, this review is focused on the application of the ZIF-8 in bone tissue engineering. This work includes an explanation of metal-organic frameworks (MOFs) and ZIF-8 including synthesis methods as well as biocompatibility and biomedical applications of ZIF-8. In fact, a literature review is provided on previous applications of ZIF-8 in bone tissue engineering. Also, the investigations related to employing ZIF-8 in bone scaffolds and drug delivery systems for the bone tissues are discussed, and future perspectives are also emphasized.

Design of metal-mediated protein assemblies via hydroxamic acid functionalities.

The self-assembly of proteins into sophisticated multicomponent assemblies is a hallmark of all living systems and has spawned extensive efforts in the construction of novel synthetic protein architectures with emergent functional properties. Protein assemblies in nature are formed via selective association of multiple protein surfaces through intricate noncovalent protein-protein interactions, a challenging task to accurately replicate in the de novo design of multiprotein systems. In this protocol, we describe the application of metal-coordinating hydroxamate (HA) motifs to direct the metal-mediated assembly of polyhedral protein architectures and 3D crystalline protein-metal-organic frameworks (protein-MOFs). This strategy has been implemented using an asymmetric cytochrome cb562 monomer through selective, concurrent association of Fe3+ and Zn2+ ions to form polyhedral cages. Furthermore, the use of ditopic HA linkers as bridging ligands with metal-binding protein nodes has allowed the construction of crystalline 3D protein-MOF lattices. The protocol is divided into two major sections: (1) the development of a Cys-reactive HA molecule for protein derivatization and self-assembly of protein-HA conjugates into polyhedral cages and (2) the synthesis of ditopic HA bridging ligands for the construction of ferritin-based protein-MOFs using symmetric metal-binding protein nodes. Protein cages are analyzed using analytical ultracentrifugation, transmission electron microscopy and single-crystal X-ray diffraction techniques. HA-mediated protein-MOFs are formed in sitting-drop vapor diffusion crystallization trays and are probed via single-crystal X-ray diffraction and multi-crystal small-angle X-ray scattering measurements. Ligand synthesis, construction of HA-mediated assemblies, and post-assembly analysis as described in this protocol can be performed by a graduate-level researcher within 6 weeks.

3D Metal-Organic Frameworks Based on Co(II) and Bithiophendicarboxylate: Synthesis, Crystal Structures, Gas Adsorption, and Magnetic Properties.

Three new 3D metal-organic porous frameworks based on Co(II) and 2,2'-bithiophen-5,5'-dicarboxylate (btdc2-) [Co3(btdc)3(bpy)2]·4DMF, 1; [Co3(btdc)3(pz)(dmf)2]·4DMF·1.5H2O, 2; [Co3(btdc)3(dmf)4]∙2DMF∙2H2O, 3 (bpy = 2,2'-bipyridyl, pz = pyrazine, dmf = N,N-dimethylformamide) were synthesized and structurally characterized. All compounds share the same trinuclear carboxylate building units {Co3(RCOO)6}, connected either by btdc2- ligands (1, 3) or by both btdc2- and pz bridging ligands (2). The permanent porosity of 1 was confirmed by N2, O2, CO, CO2, CH4 adsorption measurements at various temperatures (77 K, 273 K, 298 K), resulted in BET surface area 667 m2⋅g-1 and promising gas separation performance with selectivity factors up to 35.7 for CO2/N2, 45.4 for CO2/O2, 20.8 for CO2/CO, and 4.8 for CO2/CH4. The molar magnetic susceptibilities χp(T) were measured for 1 and 2 in the temperature range 1.77-330 K at magnetic fields up to 10 kOe. The room-temperature values of the effective magnetic moments for compounds 1 and 2 are µeff (300 K) ≈ 4.93 µB. The obtained results confirm the mainly paramagnetic nature of both compounds with some antiferromagnetic interactions at low-temperatures T < 20 K in 2 between the Co(II) cations separated by short pz linkers. Similar conclusions were also derived from the field-depending magnetization data of 1 and 2.

Studies on metal-organic framework (MOF) nanomedicine preparations of sildenafil for the future treatment of pulmonary arterial hypertension.

Pulmonary arterial hypertension (PAH) is an incurable disease, although symptoms are treated with a range of dilator drugs. Despite their clinical benefits, these drugs are limited by systemic side-effects. It is, therefore, increasingly recognised that using controlled drug-release nanoformulation, with future modifications for targeted drug delivery, may overcome these limitations. This study presents the first evaluation of a promising nanoformulation (highly porous iron-based metal-organic framework (MOF); nanoMIL-89) as a carrier for the PAH-drug sildenafil, which we have previously shown to be relatively non-toxic in vitro and well-tolerated in vivo. In this study, nanoMIL-89 was prepared and charged with a payload of sildenafil (generating Sil@nanoMIL-89). Sildenafil release was measured by Enzyme-Linked Immunosorbent Assay (ELISA), and its effect on cell viability and dilator function in mouse aorta were assessed. Results showed that Sil@nanoMIL-89 released sildenafil over 6 h, followed by a more sustained release over 72 h. Sil@nanoMIL-89 showed no significant toxicity in human blood outgrowth endothelial cells for concentrations up to100µg/ml; however, it reduced the viability of the human pulmonary artery smooth muscle cells (HPASMCs) at concentrations > 3 µg/ml without inducing cellular cytotoxicity. Finally, Sil@nanoMIL-89 induced vasodilation of mouse aorta after a lag phase of 2-4 h. To our knowledge, this study represents the first demonstration of a novel nanoformulation displaying delayed drug release corresponding to vasodilator activity. Further pharmacological assessment of our nanoformulation, including in PAH models, is required and constitutes the subject of ongoing investigations.

Co-Administration of iRGD with Sorafenib-Loaded Iron-Based Metal-Organic Framework as a Targeted Ferroptosis Agent for Liver Cancer Therapy.

PURPOSE: Hepatocellular carcinoma (HCC) is one of the most common fatal cancers, with no curative therapy available. The concept of ferroptosis is attracting increasing attention in cancer research. Herein, we describe the use of a nanodevice as an effective strategy for inducing ferroptosis to manage HCC. METHODS: To improve ferroptosis-induced treatment of HCC, we constructed sorafenib (sor)-loaded MIL-101(Fe) nanoparticles (NPs) [MIL-101(Fe)@sor] and evaluated the efficacy of ferroptosis-based HCC therapy after co-administration with the iRGD peptide both in vitro and in vivo. RESULTS: The prepared MIL-101(Fe) NPs have several promising characteristics including drug-loading, controllable release, peroxidase activity, biocompatibility, and T2 magnetic resonance imaging ability. MIL-101(Fe)@sor NPs significantly induced ferroptosis in HepG2 cells, increased the levels of lipid peroxidation and malondialdehyde, and reduced those of glutathione and glutathione peroxidase 4 (GPX-4). The in vivo results showed that the MIL-101(Fe)@sor NPs significantly inhibited tumor progression and decreased GPX-4 expression levels, with negligible long-term toxicity. Meanwhile, co-administration of MIL-101(Fe)@sor NPs with iRGD significantly accelerated ferroptosis. CONCLUSION: Our findings suggest that MIL-101(Fe)@sor NPs co-administered with iRGD are a promising strategy for inducing HCC ferroptosis.

Zinc-Based Metal-Organic Frameworks in Drug Delivery, Cell Imaging, and Sensing.

The design and structural frameworks for targeted drug delivery of medicinal compounds and improved cell imaging have been developed with several advantages. However, metal-organic frameworks (MOFs) are supplemented tremendously for medical uses with efficient efficacy. These MOFs are considered as an absolutely new class of porous materials, extensively used in drug delivery systems, cell imaging, and detecting the analytes, especially for cancer biomarkers, due to their excellent biocompatibility, easy functionalization, high storage capacity, and excellent biodegradability. While Zn-metal centers in MOFs have been found by enhanced efficient detection and improved drug delivery, these Zn-based MOFs have appeared to be safe as elucidated by different cytotoxicity assays for targeted drug delivery. On the other hand, the MOF-based heterogeneous catalyst is durable and can regenerate multiple times without losing activity. Therefore, as functional carriers for drug delivery, cell imaging, and chemosensory, MOFs' chemical composition and flexible porous structure allowed engineering to improve their medical formulation and functionality. This review summarizes the methodology for fabricating ultrasensitive and selective Zn-MOF-based sensors, as well as their application in early cancer diagnosis and therapy. This review also offers a systematic approach to understanding the development of MOFs as efficient drug carriers and provides new insights on their applications and limitations in utility with possible solutions.

Fabrication of covalent organic frameworks and its selective extraction of fluoronitrobenzenes from environmental samples.

In this study, porous covalent organic frameworks (COFs, named as COFs-SWMU) were synthesized for the first time via a facile approach by using 4,4',4''-methylidynetri-anilin and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde as precursors under ambient temperature. The COFs-SWMU were characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy, thermogravimetric analysis, etc. The COFs-SWMU exhibited a relatively high specific surface area and desirable thermal stability. The adsorption performance of COFs-SWMU towards fluoronitrobenzenes (FNBs, including 1-fluoro-2-nitrobenzene, 1-fluoro-3-nitrobenzene, 1-fluoro-4-nitrobenzene, 2,4-difluoronitrobenzene, 3,4-difluoronitrobenzene, and 3,4-dinitrofluorobenzene) was investigated on the basis of adsorption capacity and partition coefficient (PC). The adsorption kinetics and isotherm of COFs-SWMU for FNBs were studied in detail. Further, a simple, fast and sensitive method which combined COFs-SWMU based extraction with high-performance liquid chromatography-diode array detection, was proposed for the analysis of FNBs in environmental samples. Desirable linearity (R2>0.9998) in the range of 0.1-100 µg•mL-1, low limits of detection (LODs; 0.1‒0.15 µg•mL‒1), low limits of quantitation (LOQs; 0.28‒0.40 µg•mL‒1), and desirable precision (RSDs, 0.24-2.83% for intraday and 1.13-6.92% for interday) are obtained. Finally, the COFs-SWMU were applied to the effective extraction of FNBs from environmental samples, and desirable recovery results were obtained.

An Effective Hybrid Heterogeneous Catalyst to Desulfurize Diesel: Peroxotungstate@Metal-Organic Framework.

A peroxotungstate composite comprising the chromium terephthalate metal-organic framework MIL-101(Cr) and the Venturello peroxotungstate [PO4{WO(O2)2}4]3- (PW4) has been prepared by the impregnation method. The PW4@MIL-101(Cr) composite presents high catalytic efficiency for oxidative desulfurization of a multicomponent model diesel containing the most refractory sulfur compounds present in real fuels (2000 ppm of total S). The catalytic performance of this heterogeneous catalyst is similar to the corresponding homogeneous PW4 active center. Desulfurization efficiency of 99.7% was achieved after only 40 min at 70 °C using H2O2 as an oxidant and an ionic liquid as an extraction solvent ([BMIM]PF6, 2:1 model diesel/[BMIM]PF6). High recycling and reusing capacity was also found for PW4@MIL-101(Cr), maintaining its activity for consecutive oxidative desulfurization cycles. A comparison of the catalytic performance of this peroxotungstate composite with others previously reported tungstate@MIL-101(Cr) catalysts indicates that the presence of active oxygen atoms from the peroxo groups promotes a higher oxidative catalytic efficiency in a shorter reaction time.

Covalent Organic Framework Composites: Synthesis and Analytical Applications.

In the recent years, composite materials containing covalent organic frameworks (COFs) have raised increasing interest for analytical applications. To date, various synthesis techniques have emerged that allow for the preparation of crystalline and porous COF composites with various materials. Herein, we summarize the most common methods used to gain access to crystalline COF composites with magnetic nanoparticles, other oxide materials, graphene and graphene oxide, and metal nanoparticles. Additionally, some examples of stainless steel, polymer, and metal-organic framework composites are presented. Thereafter, we discuss the use of these composites for chromatographic separation, environmental remediation, and sensing.

PEG-modified lipase immobilized onto NH2-MIL-53 MOF for efficient resolution of 4-fluoromandelic acid enantiomers.

A new heterogeneous bio-catalyst was prepared by the immobilization of lipase from Pseudomonas fluorescents (PFL) onto metal-organic frameworks (MOF), NH2-MIL-53(Fe), using covalent cross-linking. The immobilized lipase [PEG-PFL@NH2-MIL-53(Fe)] was firstly applied in enantioselective resolution of 4-fluoromandelic acid (4-FMA) enantiomers. After optimization of the immobilization PFL onto NH2-MIL-53, its loading capacity is 224.5 mg PFL/g MOF. The optimal enzymatic conditions are temperature of 50 °C, VA/4-FMA substrate ratio of 6:1, immobilized lipase loading of 60 mg and reaction time of 12 h. Experimental results show that the catalytic activity and thermal stability of PFL are significantly improved by polyethylene glycol (PEG) modification and immobilization. At 65 °C, the catalytic activity of immobilized lipase retains 86.0% of initial activity. Under the optimal conditions, the excellent results were obtained with conversion of 49.6% and enantiomer excess of 98.0% for the immobilized PFL catalyzed transesterification reaction. Furthermore, the immobilized lipase exhibits excellent cycle stability with 83% of its initial activity after four cycle.

Core-shell structured magnetic covalent organic frameworks for magnetic solid-phase extraction of diphenylamine and its analogs.

Core-shell structured magnetic covalent organic frameworks (Fe3O4@COFs) were synthesized via a facile approach at room temperature using 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,5-dibromo-1,4-benzenedicarboxaldehyde (DBDA) as two building blocks for the first time. The Fe3O4@COFs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), nitrogen adsorption-desorption isotherms, and zeta potentiometric analysis. The Fe3O4@COFs had a high specific surface area (141.94 m2·g-1) and uniform pore size distribution (average 4.53 nm). They also demonstrated good magnetic response (32.49 emu·g-1) and good thermal and chemical stabilities. Furthermore, adsorption experiments were conducted to evaluate the adsorption capacities and adsorption times of Fe3O4@COFs to diphenylamine (DPA) and its analogs, including benzidine (BZ), 1-naphthylamine (1-NA), 4-phenylphenol (4-PP), and O-tolidine (O-TD). From the experimental results, the maximum adsorption capacities of DPA, 1-NA, 4-PP, BZ, and O-TD were calculated as 246.25, 95.20, 85.85, 107.20, and 123.55 mg·g-1, respectively. A duration of 20 min was sufficient for adsorption. The Fe3O4@COFs were explored as adsorbents for magnetic solid-phase extraction (MSPE) of DPA and its analogs, and the MSPE parameters, including adsorbent dosage, extraction time, pH, ionic strength, desorption solvent, desorption time, and desorption frequency were optimized. Combined with HPLC using diode-array detection, a simple, fast, and sensitive method was proposed to detect DPA and its analogs, which exhibited good linearity (r >0.9946) in the range of 0.1-100 µg·mL-1. Moreover, the low limits of detection (ranging from 0.02 to 0.08 µg·mL-1, S/N = 3), low limits of quantitation (ranging from 0.05 to 0.30 µg·mL-1, S/N = 10), good precision with low relative SDs (<5.86% for intra-day and <6.44% for inter-day) were obtained. Finally, Fe3O4@COFs were applied to the effective MSPE of DPA and its analogs in actual samples chosen from the natural environment, and good recoveries (ranging from 79.97 to 122.52%) were observed.

Covalent Organic Frameworks in Sample Preparation.

Covalent organic frameworks (COFs) can be classified as emerging porous crystalline polymers with extremely high porosity and surface area size, and good thermal stability. These properties have awakened the interests of many areas, opening new horizons of research and applications. In the Analytical Chemistry field, COFs have found an important application in sample preparation approaches since their inherent properties clearly match, in a good number of cases, with the ideal characteristics of any extraction or clean-up sorbent. The review article is meant to provide a detailed overview of the different COFs that have been used up to now for sample preparation (i.e., solid-phase extraction in its most relevant operational modes-conventional, dispersive, magnetic/solid-phase microextraction and stir-bar sorptive extraction); the extraction devices/formats in which they have been applied; and their performances and suitability for this task.

MnO2/rGO/CNTs Framework as a Sulfur Host for High-Performance Li-S Batteries.

Lithium-sulfur batteries are very promising next-generation energy storage batteries due to their high theoretical specific capacity. However, the shuttle effect of lithium-sulfur batteries is one of the important bottlenecks that limits its rapid development. Herein, physical and chemical dual adsorption of lithium polysulfides are achieved by designing a novel framework structure consisting of MnO2, reduced graphene oxide (rGO), and carbon nanotubes (CNTs). The framework-structure composite of MnO2/rGO/CNTs is prepared by a simple hydrothermal method. The framework exhibits a uniform and abundant mesoporous structure (concentrating in ~12 nm). MnO2 is an α phase structure and the α-MnO2 also has a significant effect on the adsorption of lithium polysulfides. The rGO and CNTs provide a good physical adsorption interaction and good electronic conductivity for the dissolved polysulfides. As a result, the MnO2/rGO/CNTs/S cathode delivered a high initial capacity of 1201 mAh g-1 at 0.2 C. The average capacities were 916 mAh g-1, 736 mAh g-1, and 547 mAh g-1 at the current densities of 0.5 C, 1 C, and 2 C, respectively. In addition, when tested at 0.5 C, the MnO2/rGO/CNTs/S exhibited a high initial capacity of 1010 mAh g-1 and achieved 780 mAh g-1 after 200 cycles, with a low capacity decay rate of 0.11% per cycle. This framework-structure composite provides a simple way to improve the electrochemical performance of Li-S batteries.

Highly bioactive zeolitic imidazolate framework-8-capped nanotherapeutics for efficient reversal of reperfusion-induced injury in ischemic stroke.

Rational design of potent antioxidative agent with high biocompatibility is urgently needed to treat ischemic reperfusion-induced ROS-mediated cerebrovascular and neural injury during ischemia strokes. Here, we demonstrate an in situ synthetic strategy of bioactive zeolitic imidazolate framework-8-capped ceria nanoparticles (CeO2@ZIF-8 NPs) to achieve enhanced catalytic and antioxidative activities and improved stroke therapeutic efficacy. This nanosystem exhibits prolonged blood circulation time, reduced clearance rate, improved BBB penetration ability, and enhanced brain accumulation, where it effectively inhibits the lipid peroxidation in brain tissues in middle cerebral artery occlusion mice and reduces the oxidative damage and apoptosis of neurons in brain tissue. CeO2@ZIF-8 also suppresses inflammation- and immune response-induced injury by suppressing the activation of astrocytes and secretion of proinflammatory cytokines, thus achieving satisfactory prevention and treatment in neuroprotective therapy. This study also sheds light on the neuroprotective action mechanisms of ZIF-8-capped nanomedicine against reperfusion-induced injury in ischemic stroke.

Restriction of intramolecular motions (RIM) by metal-organic frameworks for electrochemiluminescence enhancement:2D Zr12-adb nanoplate as a novel ECL tag for the construction of biosensing platform.

Herein, a new phenomenon of enhanced electrochemiluminescence (ECL) emission by restricting intramolecular motion in the 2D ultra-thin Zr12-adb (adb = 9,10-anthracene dibenzoate) metal-organic framework (MOF) nanoplate was discovered for the first time. The coordination immobilization of adb in porous ultra-thin Zr12-adb nanoplate endowed the Zr12-adb excellent ECL performance, including stronger ECL signal and higher ECL efficiency relative to those of H2adb monomers and H2adb aggregates. In the 2D Zr12-adb nanoplate, the bridging ligand adb was stretched and fixed between two Zr12 clusters, which restricted intramolecular rotations and suppressed unnecessary energy loss caused by self-rotation, thereby remarkably improved the ECL intensity and efficiency. More importantly, the porous ultra-thin structure of Zr12-adb MOF nanoplate not only allowed the coreactants to diffuse into the MOF interior, making both internal and external adb be excited, but also shortened the migration distance of electrons, ions, coreactants and coreactant intermediates, which further improved the ECL efficiency of Zr12-adb and overcame the shortcoming of H2adb aggregates in which the internal luminophores were not easily excited. Regarding the excellent ECL properties above, Zr12-adb nanoplate was selected as a new ECL emitter incorporated with the bipedal walking molecular machine together to fabricate a biosensor for sensitive detection of mucin 1. The enhanced ECL by restriction of intramolecular motions in MOFs provided a new pathway to improve ECL intensity and efficiency, which lighted up a lamp for the design and manufacture of high-performance ECL materials based on MOFs, thus offering new opportunities to develop ultrasensitive ECL biosensors.

Novel Elastically Stretchable Metal-Organic Framework Laden Hydrogel with Pearl-Net Microstructure and Freezing Resistance through Post-Synthetic Polymerization.

Nanocomposite hydrogels (NCs) with mechanical properties suitable for a diverse range of applications can be made by combining polymer hydrogel networks with various inorganic nanoparticles. However, the mechanical properties and functions of conventional NCs are seriously limited by the poor structural or functional tunability of common nanofillers and by the low amounts of such fillers that can be added. Here, the fabrication of novel elastically stretchable and compressible nanocomposite hydrogels (MIL-101-MAAm/PAAm) with a distinctive pearl-net microstructure and a metal-organic framework (MOF) content in the range of 20-60 wt% through post-synthetic polymerization (PSP) is reported. The MOFs, which are compatible with polymers and have a high degree of modifiability in structure and functions, are used as nanofillers. Such MOF-laden hydrogels can withstand 500% tensile strain or 90% compressive strain without fracture and recover quickly upon unloading. They are also resistant to freezing at -25 °C. In addition, the problems associated with poor flexibility and processability of MOFs are overcome by the hybridization of hydrogel polymer matrices with MOFs. The results of this work not only provide a new perspective on preparing NCs but also indicate a promising path for applying MOFs in flexible devices.

Swell and Destroy: A Metal-Organic Framework-Containing Polymer Sponge That Immobilizes and Catalytically Degrades Nerve Agents.

Organophosphorus chemical warfare agents function as potent neurotoxins. Whilst the destruction of nerve agents is most readily achieved by hydrolysis, their storage and transport are hazardous and lethal in milligram doses, with any spillage resulting in fatalities. Furthermore, current decontamination and remediation measures are limited by a need for stoichiometric reagents, solvents, and buffered solutions, complicating the process for the treatment of bulk contaminants. Herein, we report a composite polymer material capable of rendering bulk VX unusable by immobilization within a porous polymer until a metal-organic framework (MOF) catalyst fully hydrolyzes the neurotoxin. This is an all-in-one capability that minimizes the use of multiple reagents, facilitated by a porous high internal phase emulsion-based polystyrene monolith housing an active zirconia MOF catalyst (MOF-808); the porous polymer absorbs and immobilizes the liquid agents, while the MOF enables hydrolysis. The dichotomous hierarchy of porous materials facilitates the containment and rapid hydrolysis of VX (>80% degradation in 8 h) in the presence of excess H2O. This composite can further enable the hydrolysis of neat VX with reliance on ambient humidity (>95% in 11 days). Potentially, 4.5 kg of the composite can absorb, immobilize, and degrade the contents of a standard chemical drum/barrel (208 L, 55 gal) of the chemical warfare agent (CWA). We believe that this composite is the first example of what will be the go-to approach for CWA immobilization and degradation in the future. Furthermore, we believe that this demonstration of a catalytically reusable absorbent sponge provides a signpost for the development of similar materials where immobilization of a substrate in a catalytically active environment is desirable.