Templated interfacial synthesis of metal-organic framework (MOF) nano- and micro-structures with precisely controlled shapes and sizes

Metal-organic frameworks: synthesis, properties, wound dressing, challenges and scopes in advanced wound dressing

Wound healing is a critical but complex biological process of skin tissue repair and regeneration resulting from various systems working together at the cellular and molecular levels. Quick wound healing and the problems associated with traditional wound repair techniques are being overcome with multifunctional materials. Over time, this research area has drawn significant attention. Metal-organic frameworks (MOFs), owning to their peculiar physicochemical characteristics, are now considered a promising class of well-suited porous materials for wound healing in addition to their other biological applications. This detailed literature review provides an overview of the latest developments in MOFs for wound healing applications. We have discussed the synthesis, essential biomedical properties, wound-healing mechanism, MOF-based dressing materials, and their wound-healing applications. The possible major challenges and limitations of MOFs have been discussed, along with conclusions and future perspectives. This overview of the literature review addresses MOFs-based wound healing from several angles and covers the most current developments in the subject. The readers may discover how the MOFs advanced this discipline by producing more inventive, useful, and successful dressings. It influences the development of future generations of biomaterials for the healing and regeneration of skin wounds.

Recent advances in metal organic frameworks-based magnetic nanomaterials for waste water treatment

Magnetic nanoparticle-incorporated metal organic frameworks (MOF) are potential composites for various applications such as catalysis, water treatment, drug delivery, gas storage, chemical sensing, and heavy metal ion removal. MOFs exhibits high porosity and flexibility enabling guest species like heavy metal ions to diffuse into bulk structure. Additionally, shape and size of the pores contribute to selectivity of the guest materials. Incorporation of magnetic materials allows easy collection of adsorbent materials from solution system making the process simple and cost-effective. In view of the above advantages in the present review article, we are discussing recent advances of different magnetic material-incorporated MOF (Mg-MOF) composite for application in photocatalytic degradation of dyes and toxic chemicals, adsorption of organic compounds, adsorption of heavy metal ions, and adsorption of dyes. The review initially discusses on properties of Mg-MOF, different synthesis techniques such as mechanochemical, sonochemical (ultrasound) synthesis, slow evaporation and diffusion methods, solvo(hydro)-thermal and iono-thermal method, microwave-assisted method, microemulsion method post-synthetic modification template strategies and followed by application in waste water treatment.

Photovoltaic performance of MOF-derived transition metal doped titania-based photoanodes for DSSCs

The enduring effort toward stabilizing and improving the efficiency of dye-sensitized solar cells (DSSCs) has stirred the solar research community to follow innovative approaches. Current research centered on electrode materials design, which improves photoanodes' light-harvesting efficiency (LHE). Metal-Organic Frameworks (MOFs) are a new family of materials that can be used as competent materials due to their desirable qualities, including high porosity, flexible synthesis methodology, high thermal and chemical stability, and good light-harvesting capabilities. MOF-derived porous photoanodes can effectively adsorb dye molecules and improve LHE, resulting in high power conversion efficiency (PCE). Doping is a prospective methodology to tune the bandgap and broaden spectral absorption. Hence, a novel and cost-effective synthesis of high surface area transition metal (TM) doped TiO₂ nanocrystals (NCs) via the metal-organic framework route for DSSCs is reported here. Among the TM dopants (i.e., Mn, Fe, Ni), a remarkable PCE of 7.03% was obtained for nickel-doped samples with increased Jsc (14.66 mA/cm²) due to the bandgap narrowing and porous morphology of TiO₂. The findings were further confirmed using electrochemical impedance spectroscopy (EIS) and dye-desorption experiments. The present study expedites a promising way to enhance the LHE for many innovative optoelectronic devices.

ZIF-67 In Situ Grown on Attapulgite: A Flame Retardant Synergist for Ethylene Vinyl Acetate/Magnesium Hydroxide Composites

ZIF-67@ATP was prepared by the in situ growth of the zeolite imidazole frame (ZIF-67) on the surface of attapulgite (ATP). The structure and surface morphology of ZIF-67@ATP were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Different mass fractions of ATP and ZIF-67@ATP were added to ethylene vinyl acetate (EVA)/magnesium hydroxide (MH) composites as flame retardant synergists. The flame retardancy of EVA composites was evaluated by the limiting oxygen index (LOI) test, UL-94 test and cone calorimeter test. Composites containing 3 wt% of ZIF-67@ATP reached an LOI value of 43% and a V-0 rating in the UL-94 test, and the ignition time of the composite increased from 38 s to 56 s. The tensile strength and impact strength of the composites did not change significantly, but the elongation at break increased greatly. Typically, for composites containing 4 wt% of ZIF-67@ATP, the elongation at break of the composites increased from 69.5% to 522.2% compared to the samples without the synergist. This study provides novel insights into the application of attapulgite in the field of flame retardant polymer materials.

MOFs/Ketjen Black-Coated Filter Paper for Spontaneous Electricity Generation from Water Evaporation

Metal-organic frameworks (MOFs) have the advantages of tunable pore sizes and porosity and have demonstrated unique advantages for various applications. This study synthesized composite MOF nanomaterials by modifying MOF801 or AlOOH with UIO66. The composite nanomaterials, UIO66/MOF801 and UIO66/AlOOH showed increased Zeta potential than their pristine form, AlOOH, UIO66 and MOF801. For the first time, the composite MOFs were used to fabricate filter paper-based evaporation-driven power generators for spontaneous electricity generation. The MOFs-KBF membrane was constructed by coating filter paper (10 × 50 mm) with composite MOFs and conductive Ketjen Black. The UIO66/MOF801 decorated device achieved a maximum open circuit voltage of 0.329 ± 0.005 V and maximum output power of 2.253 μW. The influence of salt concentration (0.1-0.5 M) on power generation was also analyzed and discussed. Finally, as a proof-of-concept application, the device was employed as a salinity sensor to realize remote monitoring of salinity. This work demonstrated the potential of flexible MOF composites for spontaneous power generation from water evaporation and provides a potential way to enhance the performance of evaporation-driven power generators.

Growth Pattern Control and Nanoarchitecture Engineering of Metal-Organic Framework Single Crystals by Confined Space Synthesis

The nanoarchitecture engineering of metal-organic frameworks (MOFs) is a fascinating but intellectually challenging concept that opens up avenues for both tailoring the properties of MOFs and expanding their applications. Herein, we report the confined growth of ZIF-8 single crystals in a three-dimensionally ordered (3DO) macroporous polystyrene replica and reveal that their growth patterns, morphologies, and nanoarchitectures can be highly engineered using the concentration of the precursor. Impressively, the favorable in situ confined growth enables the successful fabrication of 3DO sphere-assembled ZIF-8 single crystals or 3DO single-crystalline ZIF-8 sphere arrays when a low- or high-concentration precursor solution, respectively, is used as the feedstock. Furthermore, our strategy can be extended to the preparation of other 3DO MOF single crystals, including ZIF-67 and HKUST-1, with similar controllable hierarchical nanoarchitectures. With the successful preparation of a series of diameter-tunable ZIF-8 single-crystalline spheres, we further unravel their interesting size-performance relationship in the Knoevenagle reaction between benzaldehyde and malononitrile, wherein the smallest spheres show the fastest first-order reaction kinetics. This study not only develops a general strategy for engineering the nanoarchitectures of MOF single crystals but also provides fundamental knowledge of the mechanism for the growth of hierarchical single crystals under confined spaces.

Application of Fiber Biochar-MOF Matrix Composites in Electrochemical Energy Storage

Fiber biochar-metal organic framework (MOF) composites were successfully prepared by three different biochar preparation methods, namely, the ionic liquid method, the pyrolysis method, and the direct composite method. The effects of the different preparation methods of fiber biochar on the physical and chemical properties of the biochar-MOF composites showed that the composite prepared by the ionic liquid method with the Zeolite-type imidazolate skeleton -67 (ZIF-67) composite after high temperature treatment exhibited a better microstructure. Electrochemical tests showed that it had good specific capacity, a fast charge diffusion rate, and a relatively good electrochemical performance. The maximum specific capacity of the composite was 63.54 F/g when the current density was 0.01 A/g in 1 mol/L KCl solution. This work explored the preparation methods of fiber biochar-MOF composites and their application in the electrochemical field and detailed the relationship between the preparation methods of the composites and the electrochemical properties of the electrode materials.

Cooperative Effect of ZIF-67-Derived Hollow NiCo-LDH and MoS2 on Enhancing the Flame Retardancy of Thermoplastic Polyurethane

In this work, a novel three-dimensional (3D) hollow nickel-cobalt layered double hydroxide (NiCo-LDH) was synthesized using zeolitic imidazole framework-67 (ZIF-67) as a template, and then utilized to functionalize molybdenum disulfide (NiCo-LDH/MoS2) via electrostatic force. Flame retardant thermoplastic polyurethane (TPU) composites were prepared by the melt blending method. Compared to pure TPU, NiCo-LDH/MoS2 filled TPU composite was endowed with a decrease of 30.9% and 55.7% of the peak heat release rate (PHRR) and the peak smoke production rate (PSPR), respectively. Furthermore, the addition of NiCo-LDH/MoS2 can significantly improve the thermal stability and char yield of the TPU composite. The catalytic carbonization effect and dilution effect of NiCo-LDH, and the barrier effect of MoS2 nanosheets enable TPU composites with excellent flame retardancy and toxic gas suppression ability.

Morphology-Controlled Synthesis of Polyphosphazene-Based Micro- and Nano-Materials and Their Application as Flame Retardants

Common flame retardants, such as halogen-based materials, are being phased-out owing to their harmful environmental and health effects. We prepared poly-(cyclotriphosphazene-co-4,4'-sulfonyldiphenol) (PZS) microspheres, nanotubes, capsicum-like nanotubes, and branched nanotubes as flame retardants. An increase in reaction temperature changed the morphology from nanotubes to microspheres. A PZS shape had a positive effect on the flame retardancy of polyethylene terephthalate (PET). The PZS with a capsicum-like nanotube morphology had the best flame retardancy, and the PET limiting oxygen index increased from 25.2% to 34.4%. The flame retardancy capability was followed by PZS microspheres (33.1%), branched nanotubes (32.8%), and nanotubes (32.5%). The capsicum-like nanotubes promote the formation of highly dense and continuous carbon layers, and they release a non-combustible gas (CO2). This study confirms polyphosphazene-based flame retardants as viable and environmentally-friendly alternatives to common flame retardants. It also presents a novel and facile design and synthesis of morphology-controlled nanomaterials with enhanced flame retardant properties.

Carboxymethyl Cellulose/Zn-Organic Framework Down-Regulates Proliferation and Up-Regulates Apoptosis and DNA Damage in Colon and Lung Cancer Cell Lines

A solvothermal technique was used to prepare a Zn-benzenetricarboxylic acid (Zn@BTC) organic framework covered with a carboxymethyl cellulose (CMC/Zn@BTC). Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and Brunauer, Emmett, and Teller (BET) surface area were applied to characterize CMC/Zn@BTC. Moreover, the anticancer, anti-migrative, anti-invasive, and anti-proliferative action of CMC/Zn@BTC nanoparticles were assessed on cancer cell lines. Apoptotic markers and DNA damage were assessed to explore the cellular and biological changes induced by CMC/Zn@BTC nanoparticles. The microscopic observation revealed that CMC controls the surface morphology and surface characteristics of the Zn@BTC. The obtained BET data revealed that the Zn@BTC nanocomposite surface area lowers from 1061 m2/g to 740 m2/g, and the pore volume decreases from 0.50 cm3/g to 0.37 cm3/g when CMC is applied to Zn@BTC nanocomposites. The cellular growth of DLD1 and A549 was suppressed by CMC/Zn@BTC, with IC50 values of 19.1 and 23.1 μg/mL, respectively. P53 expression was upregulated, and Bcl-2 expression was downregulated by CMC/Zn@BTC, which promoted the apoptotic process. Furthermore, CMC/Zn@BTC caused DNA damage in both cancer cell lines with diverse impact, 66 percent (A549) and 20 percent (DLD1) compared to cisplatin's 52 percent reduction. CMC/Zn@BTC has anti-invasive properties and significantly reduced cellular migration. Moreover, CMC/Zn@BTC aims key proteins associated with metastasis, proliferation and programmed cellular death.

Development of Amine-Functionalized Metal-Organic Frameworks Hollow Fiber Mixed Matrix Membranes for CO2 and CH4 Separation: A Review

CO2 separation from raw natural gas can be achieved through the use of the promising membrane-based technology. Polymeric membranes are a known method for separating CO2 but suffer from trade-offs between its permeability and selectivity. Therefore, through the use of mixed matrix membranes (MMMs) which utilizes inorganic or hybrid fillers such as metal-organic frameworks (MOFs) in polymeric matrix, the permeability and selectivity trade-off can be overcome and possibly surpass the Robeson Upper Bounds. In this study, various types of MOFs are explored in terms of its structure and properties such as thermal and chemical stability. Next, the use of amine and non-amine functionalized MOFs in MMMs development are compared in order to investigate the effects of amine functionalization on the membrane gas separation performance for flat sheet and hollow fiber configurations as reported in the literature. Moreover, the gas transport properties and various challenges faced by hollow fiber mixed matrix membranes (HFMMMs) are discussed. In addition, the utilization of amine functionalization MOF for mitigating the challenges faced is included. Finally, the future directions of amine-functionalized MOF HFMMMs are discussed for the fields of CO2 separation.

Chitosan Containing Nano Zn-Organic Framework: Synthesis, Characterization and Biological Activity

A biologically active agent based on a Zn-1,3,5-benzen tricarboxylic acid (Zn-BTC) framework incorporated into a chitosan (CS) biopolymer (Zn-BTC@CS) was successfully synthesized using a microwave irradiation technique. The synthesized Zn-BTC@CS was characterized using a scanning electron microscope (SEM) and the obtained data indicated a highly smooth surface morphology of the synthesized Zn-BTC and no morphological changes when the Zn-BTC covered the CS. In addition, the particle size diameter varied from 20 to 40 nm. XRD displayed a well-maintained Zn-BTC structure, and the crystal structure of Zn-BTC was not distorted by the composition of Zn-BTC and chitosan in the nanocomposite. Data from BET analysis revealed that the specific surface area of the Zn-BTC was reduced from 995.15 m2/g to 15.16 m2/g after coating with chitosan. The pore size distribution and pore volume of the Zn-BTC, Zn-BTC@CS were centered at 37.26 nm and at 22.5 nm, respectively. Zn-BTC@CS exhibited anticancer efficacy against lung and colon cancer cell lines. Zn-BTC@CS inhibited the proliferation of A549 and DLD-1 cancer cell lines in a dose-dependent manner with IC50 values of 13.2 and 19.8 µg/mL for the colon and lung cancer cell lines, respectively. Zn-BTC@CS stimulated the apoptotic process through up-regulating P53 expression and down-regulating Bcl-2 expression. Moreover, Zn-BTC@CS induced in vitro DNA fragmentation in both cancer cell lines with significantly different affinity by 66% (A549) and 20% (DLD-1) versus 52% reduction by Cisplatin. Zn-BTC@CS (IC50) exhibited anti-invasive activity and dramatically inhibited the migration of lung and colon cancer cell lines. This study provides evidence that Zn-BTC@CS targets the essential proteins involved in proliferation, metastasis, and apoptosis. Thus, Zn-BTC@CS has chemotherapeutic potential for inhibiting lung and colon cancer viability and growth.

Self-supported metal-organic framework-based nanostructures as binder-free electrodes for supercapacitors

Metal-organic frameworks (MOFs), an interesting class of functional inorganic materials, have recently emerged as suitable electrode materials or templates/precursors of electrode materials for supercapacitors (SCs). The key in utilizing MOF-based electrode materials is to address the low electronic conductivity and poor stability issues. Therefore, the rational design and fabrication of self-supported binder-free electrodes is considered the most promising strategy to address these challenges. In this review, we summarize the recent advances in the design and manufacture of self-supported MOF-based nanostructures and their use as binderless electrodes for SCs, especially over the last five years. The synthesis strategies for constructing pristine MOFs, MOF composites and MOF derivative arrays are overviewed. By highlighting the advantages and challenges of each class of electrode materials, we hope that this review will provide some insights into the rational design of MOF-based electrode materials to promote the future development of this highly exciting field.

Advances in Nanomaterials-Based Electrochemical Biosensors for Foodborne Pathogen Detection

Electrochemical biosensors utilizing nanomaterials have received widespread attention in pathogen detection and monitoring. Here, the potential of different nanomaterials and electrochemical technologies is reviewed for the development of novel diagnostic devices for the detection of foodborne pathogens and their biomarkers. The overview covers basic electrochemical methods and means for electrode functionalization, utilization of nanomaterials that include quantum dots, gold, silver and magnetic nanoparticles, carbon nanomaterials (carbon and graphene quantum dots, carbon nanotubes, graphene and reduced graphene oxide, graphene nanoplatelets, laser-induced graphene), metal oxides (nanoparticles, 2D and 3D nanostructures) and other 2D nanomaterials. Moreover, the current and future landscape of synergic effects of nanocomposites combining different nanomaterials is provided to illustrate how the limitations of traditional technologies can be overcome to design rapid, ultrasensitive, specific and affordable biosensors.