Zeolitic Imidazolate Framework-8 Crystals Research Articles

One-pot synthesis of a porphyrin functionalized metal-organic frameworks as a recyclable visible-light-driven photosensitizer for efficient detoxification of a sulfur mustard simulant in air

Herein, we report a facile one-pot in situ self-assembly approach that enables a porphyrin photosensitizer, [5,10,15,20-tetrakis(4-methoxycarbonylphenyl)porphyrin]-Zn(II) (ZnTPP), to be enshrouded by a zeolitic imidazolate framework-8 (ZIF-8) to afford a novel visible-light-driven heterogeneous photosensitizer, ZnTPP@ZIF-8 composite. The ZnTTP photosensitizer was well dispersed and fully confined within the ZIF-8 crystals and the framework intactness and porosity were well maintained. The as-prepared ZnTPP@ZIF-8 composite integrates the advantages of ZIF-8 MOFs and ZnTTP photosensitizer. It not only can effectively produce both singlet oxygen (1O2) and superoxide ion (∙O2−) under visible light irradiation, but also exhibit high surface area and excellent stability. The structure characterization of ZnTPP@ZIF-8 composite was first carried out, and then this material can be used as a heterogeneous photosensitizer for the rapid and highly selective detoxification of a sulfur mustard simulant (2-chloroethyl ethyl sulfide) into the corresponding much less toxic sulfoxide product with a half-life of only 1.5 min under visible light irradiation at room temperature in air atmosphere. This catalyst can be readily recycled and reused at least six times without obvious loss of catalytic activity. This study will provide us a new strategy for the facile, rapid and environmentally friendly preparation of photosensitizer@MOFs composites and the rapid detoxification of sulfur mustard under ambient conditions in the future.

Creation of Wood-Based Hierarchical Superstructures via In Situ Growth of ZIF-8 for Enhancing Mechanical Strength and Electromagnetic Shielding Performance.

Given the escalating prevalence of electromagnetic pollution, there is an urgent need for the development of high-performance electromagnetic interference (EMI) shielding materials. Herein, wood-based electromagnetic shielding materials have gained significant popularity due to their exceptional performance as building materials. In this study, a novel wood-based composite with electromagnetic shielding properties is developed. Through the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) crystals on wood fibers, coupled with uniform integration of carbon nanotubes (CNTs), a multifunctional composite named ZIF-8/Poplar-CNT composite is synthesized via a one-step thermoforming process. The incorporation of CNTs endows the composites with excellent EMI shielding effectiveness (EMI SE). Among these elements, despite ZIF-8 crystals not possessing intrinsic electromagnetic shielding functionality, their distinctive dodecahedral structure proves adept at scattering and reflecting electromagnetic waves within the composites, further improving the electromagnetic shielding effect. Hence, the ZIF-8/Poplar-CNT composite (56.95dB) has ≈10dB higher EMI SE compared to that of the composites without ZIF-8 crystals. Meanwhile, ZIF-8 crystals endow the materials with excellent tensile strength (54.84MPa, enhanced by 4 times). Moreover, the introduction of Zn2+ provides superior antibacterial properties. The potential applications of ZIF-8/Poplar-CNT composites extend to diverse areas such as building decoration, electronic products, and medical equipment.

Leveraging Diffusion Kinetics to Reverse Propane/Propylene Adsorption in Zeolitic Imidazolate Framework-8.

The separation challenge posed by propylene/propane mixtures arises from their nearly identical molecular sizes and physicochemical properties. Metal-organic frameworks (MOFs) have demonstrated potential in addressing this challenge through the precision tailoring of pore sizes and surface chemistry. However, introducing modifications at the molecular level remains a considerable hurdle. This work presents an approach to reversibly tune the propylene/propane adsorption preference in zeolitic imidazolate framework-8 (ZIF-8) by manipulating the particle size and gas flow rate. Systematically increasing the ZIF-8 crystals from 9 to 224 μm restricts propane diffusion, thereby reversing its preferential adsorption over propylene. Furthermore, raising the gas flow rate of mixed propylene/propane shifts the rate-determining breakthrough step from thermodynamic equilibrium to kinetics, again reversing the adsorption preference in a particular ZIF-8 sample. We propose "dynamic selectivity (Sd(t))" as a concept that incorporates both thermodynamic and kinetic factors to elucidate these unexpected findings. Moreover, the driving force equation, grounded on the concept of Sd(t), has improved the precision and stability of the computational simulation for fixed-bed adsorption processes. This work underscores the potential of diffusion-based modulation, implemented through manageable external changes, as a viable strategy to optimize separation performance in porous adsorbent materials.

ZIF-8-decorated wood sponge derived from biomimetic mineralization of polydopamine

Zeolitic imidazolate framework-8 (ZIF-8) is extensively researched and used because of its exclusive structural and excellent physicochemical properties; however, significant challenges of alleviating the adverse effects of its particle form in many aspects are still faced by the scientific community. In this study, in situ growth of ZIF-8 within the pore channels and surfaces of green cellulose-based wood sponge was attempted through polydopamine-mediated incubation. The wood sponge was prepared by eliminating lignin and hemicellulose from natural balsa wood. Then, the sponge was impregnated with dopamine aqueous solution to yield polydopamine-covered wood sponge (PWS). ZIF-8 crystals were ultimately in situ grown in the substrate after sequential impregnation with zinc nitrate hexahydrate and 2-methylimidazole aqueous solutions at room temperature. Additionally, the effects of the deposition concentration of the dopamine aqueous solution and ZIF-8 incubation time were investigated. The obtained ZIF-8@PWS was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, Brunauer–Emmett–Teller analysis and thermogravimetric analysis. Finally, the toluene adsorption performance of porous ZIF-8@PWS in aqueous solution was also briefly evaluated, and it was demonstrated that the maximum adsorption capacity was 106.4 mg/g and the removal rate was as high as 94.2%. This work validates the envisioned universal protocol of preparing ZIF-8-decorated porous substrates through the integrated mediating role of polydopamine.

High-efficiency air filter aerogel resembling blood cell with heterogeneous epitaxial growth of zeolitic imidazolate framework-8 anchored on tunicate cellulose nanofibers for integrated air cleaning

Metal-organic frameworks (MOFs) possess highly ordered porous structures and photocatalytic capabilities, making them ideal for air cleaning and antibacterial applications. However, the crystallization kinetics of MOFs constrain their crystal structure, which limits their practical usage for air cleaning and other applications. Herein, we present a non-MOF template strategy to achieve heterogeneous epitaxial growth of zeolitic imidazolate framework-8 (ZIF-8) on cellulose extracted from tunicate. TEMPO-oxidation tunicate cellulose nanofibers (TOCNFs) have a high length-diameter ratio (>1000) and negatively charged carboxyl and hydroxyl groups that serve as suitable templates to promote heterogeneous nucleation of the ZIF-8 crystal, thereby resulting in the fabrication of a unique porous structure resembling blood cell. The ZIF-8@TOCNFs aerogel shows good porosity performance, achieving a maximum particulate matter (PM) removal efficiency of 95.80 % with a low pressure drop of 14 Pa at an air-flow velocity of 0.34 m/s. Compared to other works and commercial filters, ZIF-8@TOCNFs aerogel exhibits a higher quality factor (QF) of up to 0.197 Pa−1. Furthermore, ZIF-8@TOCNFs aerogel also demonstrates remarkable antibacterial and antiviral performance without UV photocatalysis. This unique design of ZIF-8@TOCNFs aerogel opens a new avenue for non-MOF template growth of MOF-on-MOF heterostructures and provides a novel strategy for preparing high-performance air filters with an integrated performance of low pressure drop, high removal efficiency and QF, great antibacterial and antiviral properties.

Synthesis and potential osteogenic applications of Wnt3a‐loaded ZIF‐8 nanoparticles

The Wnt signaling pathway plays a critical role in bone homeostasis, and the related protein therapy strategies have been reported to have great potential in osseointegration; however, they face formidable challenges such as complex external environments and unavoidable protein denaturation. In this work, we report a novel approach combining the synthesis of metal–organic frameworks (MOFs) and protein encapsulation in a one-pot process based on zeolitic imidazolate framework-8 (ZIF-8) and Wnt3a protein, with improved biomechanical behavior and enhanced protein biological response. This combination was designed to enhance the Wnt3a protein function through the improved chemical stability provided by the ZIF-8 crystals. Additionally, the zinc ions contained in the ZIF-8 crystals induced bone homeostasis, further favoring the osteogenesis. The results showed that the Wnt3a protein-loaded ZIF-8 crystals served as efficient drug delivery vehicles to promote osteogenesis, preventing protein denaturation. In particular, Wnt3a-loaded ZIF-8 nanoparticles (Wnt3a@ZIF-8 NPs) had higher efficacy on bone marrow mesenchymal stem cells (BMSCs) than ZIF-8 NPs or Wnt3a proteins, contributing to the osteogenesis through ZIF-8 crystals and intracellular Wnt3a proteins released from Wnt3a@ZIF-8 NPs. Furthermore, polymerase chain reaction (PCR) analysis showed that the osteogenic pathways were upregulated. Overall, the present one-pot process can open up new avenues to develop signaling protein-delivery systems for applications in protein therapy strategies.

Fabrication of well-intergrown ZIF-8 films via sequential ZnO seed layer overlaying

The fabrication of well-intergrown metal–organic frameworks (MOFs) in film morphology is crucial for various applications such as gas separation and sensing, as it necessitates uniform and controlled mass transport and sorption at the internal pore surfaces. In this work, we report the growth of continuous zeolitic imidazolate framework-8 (ZIF-8) thin films via a secondary solvothermal growth method using a consecutive ZnO seed layer overlaying approach. The primary growth of ZIF-8 crystals on planar substrates occurs through heterogeneous nucleation in solution, followed by overlaying ZnO seed layers via radio frequency (RF) sputtering for secondary growth. We systematically investigate the morphology, crystallinity, and surface properties of the resulting ZIF-8 films. Our results confirm that the seed layer overlaying induces core–shell-like growth on the primary ZIF-8 crystals, promoting conformal growth and interconnection between isolated islands. These findings demonstrate a promising method for synthesizing continuous, well-intergrown MOF films with high surface coverage with various compositions and porosities for numerous applications.

Removal of Low Trace ppb-Level Perfluorooctanesulfonic Acid (PFOS) with ZIF-8 Coatings Involving Adsorbent Degradation.

For the first time, low trace-level removal of perfluorooctanesulfonic acid (PFOS), i.e., 20-500 μg/L (ppb), from aqueous solutions using zeolitic imidazolate framework-8 (ZIF-8)-coated copper sheet (ZIF-8@Cu) composite is reported here. In comparison with different commercial activated carbon (AC) and all-silica zeolites, the composite showed the highest removal rate of 98%, which remained consistent over a wide range of concentrations. Additionally, no adsorbent leaching from the composite was noticed, which eradicated pre-analysis steps such as filtration and centrifugation, unless needed for other adsorbents studied here. The composite displayed fast uptake with saturation reaching within 4 h, irrespective of the initial concentration. However, the morphological and structural characterization revealed surface degradation of ZIF-8 crystals, along with a decline in the crystal size. The adsorption of PFOS on ZIF-8 crystals was linked to chemisorption, as the surface degradation surges with an increase in PFOS concentration or with cyclic exposure at low concentrations. Methanol seemingly removed surface debris (partially), thus providing access to ZIF-8 beneath the surface debris. Overall, the findings demonstrate that at low trace ppb-level PFOS concentrations ZIF-8 can be considered as a possible candidate for PFOS removal, even though it suffers slow surface degradation, it also removes efficiently PFOS molecules from aqueous solutions.

Copper-induced synthesis of zinc imidazolate metal-organic framework (ZIF-8) crystals and coatings

Zeolitic imidazolate framework-8 (ZIF-8) is one of the most stable Metal Organic Frameworks currently available, with promising properties in adsorption, separation and catalysis. Herein, we report a method for the rapid production of ZIF-8 crystals at room-temperature from methanolic solutions containing sodium acetate and metal salts. Of the different metal salts tested, copper nitrate presence prompted formation of cubic shaped ZIF-8 crystals within 5 min. Derived from this finding, an adaption of the synthesis route was implemented over copper foils and copper based metallic/non-metallic substrates, which yielded high quality shape- and size-controlled ZIF-8 crystal coatings. The outcomes also revealed a significant impact of sodium acetate as modulator and of copper ions released in the reaction media as triggering agent/co-modulator. Together these chemical species are understood to be involved in a multitude of coordination complex formation and deprotonation equilibria, thus largely determining the ZIF-8 crystal morphology and growth, especially near the copper releasing sites. Overall, this work presents an important platform for rapid and controlled synthesis of ZIF-8 crystals and coatings over metallic/non-metallic substrates, which can be adapted for advanced applications such as device integration.

Surfactant regulated synthesis of ZIF-8 crystals as carbonic anhydrase-mimicking nanozyme

Zeolitic imidazolate framework-8 (ZIF-8) nanozymes were successfully synthesized by using non-ionic surfactant Triton X-100 as regulator. The surfactant molecules can bind on ZIF-8 surface to modulate the nucleation and facet growth, which therefore produces ZIF-8 crystals with controlled morphology and size. The as-prepared ZIF-8 crystals reproduce the functional property of natural carbonic anhydrase (CA) by showing excellent CA-like esterase activity. The catalytic activity of ZIF-8 nanozymes was greatly enhanced at high temperature, which is superior to natural CA and is of great potential for practical applications. Moreover, the esterase activity of ZIF-8 shows great dependence on the crystal size. Basically, smaller ZIF-8 nanozymes had higher catalytic activity at a specified temperature, except for the smallest ZIF-8 crystals with size of ~50 nm that gave reduced activity due to aggregation at high temperatures of 60 or 80 °C. In addition, colorimetric experiments showed that ZIF-8 nanozymes showed similar hydration activity to that of natural CA. The study probes into the effect of nonionic surfactant on ZIF-8 synthesis as well as the abnormal size effect at higher temperature, which is of great help for the development of suitable nano-enzymes for industry applications.

Enhanced stability of Ti3C2Tx MXene enabled by continuous ZIF-8 coating

MXenes have recently attracted significant interest owing to their outstanding properties and performance. However, their hydrophilic and metastable surfaces make most MXenes prone to oxidation, which can greatly degrade their properties and hinder their practical applications. Here, we enhanced the stability of Ti3C2Tx MXene films by coating a continuous zeolitic imidazolate framework-8 (ZIF-8) layer. The high-density oxygen functional groups of MXene, which are crucial for inducing the nucleation of ZIF-8 crystals, were merged into a continuous layer on the MXene surface. 98% of the original electromagnetic interference shielding effectiveness of ZIF-8/Ti3C2Tx MXene was retained even after 4 days of harsh oxidation treatment at 85 °C and 85% RH. The enhanced stability could be attributed to the hydrophobic microporous structure of ZIF-8, which effectively hindered the permeation of water molecules in addition to terminating the dangling bonds of MXene with Zn ions.

Selenium confined in ZIF-8 derived porous carbon@MWCNTs 3D networks: tailoring reaction kinetics for high performance lithium-selenium batteries

Lithium-selenium battery is nowadays a highly competing technology to the commercial Li-ion battery because it has a high volumetric capacity of 3253 mAh cm-3 and gravimetric capacity of 675 mAh g-1. However, the practical application of lithium-selenium (Li-Se) batteries is impeded by the shuttle effect of the soluble polyselenides during the cycling process. Herein, we report the in situ growth and pyrolysis of the metal-organic framework zeolitic imidazolate framework-8 (ZIF-8) on three-dimensional (3D) interconnected highly conductive multiwalled carbon nanotubes (MWCNTs). The obtained composites are used to anchor Se for advanced Li-Se batteries. Compared with the isolated ZIF-8 derived microporous carbon, our synthesized ZIF-8 derived porous carbon@MWCNTs (ZIF-8-C@MWCNTs) 3D highly conductive networks facilitate lithium ion diffusion and electron transportation. The particle size of ZIF-8 crystals has an important impact on the battery performance. By adjusting the particle size of ZIF-8, the electrochemical reaction kinetics in ZIF-8-C@MWCNTs 3D networks can be tuned. The optimized particle size of ZIF-8 around 300-500 nm coated on MWCNTs composite achieves an excellent initial discharge capacity of 756 mAh g-1 and a stabilized capacity of 468 mAh g-1 at 0.2 C after 200 cycles. Combining the 3D MWCNTs with the appropriate size of ZIF-8 derived microporous carbon particles could highly improve the performance of the Li-Se battery. This work provides significant guidance for further structural design and host particle size selection for high-performance Li-Se batteries.

Improved stability of zeolitic imidazolate framework-8 photocatalytic coating on polyurethane foam via polyelectrolyte multilayer surface modification

Polycrystalline zeolitic imidazolate framework-8 (ZIF-8) layers have been coated on polyurethane (PU) foam substrate by a combined seed anchoring and secondary growth process. A polyelectrolyte multilayers (PEMs) primer was used to enhance the initial anchoring of the ZIF-8 seed crystals on the PU surface. X-Ray diffraction confirmed that the three-step process (PEM primer, MOF seed adsorption, secondary growth) produced a dense and homogeneous coating of ZIF-8 crystals on the PU foam substrate. The thickness of the ZIF-8 coating was observed by scanning electron microscopy (SEM) and was found to increased from 270 nm to 420 nm when the PEM primer was used when compared to the PU surface deposition. The PU/PEMs/ZIF-8/ foams were tested for their photocatalytic degradation of methylene blue (MB) under UV light and displayed a 4 folds increase in methylene blue (MB) adsorbtion over ZIF-8/PU foam. The photodegradation of MB was also increased from 31% in ZIF-8/PU to 51% in ZIF-8/PEMs/PU foams. Finally, The superior efficiency of the PEMs anchored seeds displayed outstanding photocatalytic efficiency with reusability up to 4 cycles when compared to the without PEMs modified one that lost their performance after only 1 cycle of the photodegradation test.

Peptide-Mediated Synthesis of Zeolitic Imidazolate Framework-8: Effect of Molecular Hydrophobicity, Charge Number and Charge Location.

Three amphiphilic peptides with varied molecular hydrophobicity, charge number and charge location have been designed as regulators to modulate the crystal growth of zeolitic imidazolate framework-8 (ZIF-8). All three peptides can interact with ZIF-8 to inhibit {100} facet growth and produce truncated cubic crystals. The peptide’s molecular hydrophobicity plays a dominant role in defining the final morphology and size of the ZIF-8 crystals. The peptides with less charge and higher hydrophobicity can promote nuclei formation and crystal growth to give smaller ZIF-8 crystals. However, the charge located in the center of the molecular hydrophobic region has little effect on the crystal nucleation and growth due to the shielding of its charge by molecular aggregation. The study provides insights into the effect of molecular charge and hydrophobicity on ZIF-8 crystal growth and is helpful for guiding the molecular design for regulating the synthesis of metal-organic framework materials.

Fabrication of ZIF-8 decorated copper doped TiO2 nanocomposite at low ZIF-8 loading for solar energy applications

The effects of crystallization time and amount of Zeolitic Imidazolate Framework-8 (ZIF-8) on the photocatalytic activity of ZIF-8 decorated copper (Cu) doped titania (TiO2) (ZIF-8/Cu-TiO2) powders were investigated in this study. The formation of nanocomposite structure of ZIF-8 crystals grown over the surface of core Cu-TiO2 particles containing heterojunction sites was observed at low ZIF-8 level. Powders containing ZIF-8 in the 5–46% range (weight basis) were synthesized and their activities in the photocatalytic degradation of an organic dye molecule were evaluated. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (ATR-FTIR), thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM) analyses indicated that ZIF-8/Cu-TiO2 nanocomposite can be prepared at low levels of ZIF-8. HR-TEM images of 46% ZIF-8/Cu-TiO2 showed that Cu-TiO2 particles act as a core and ZIF-8 crystals grow over the surface of Cu-TiO2 particles during crystal growth and Cu-TiO2 particles were almost completely covered with ZIF-8 crystals. Photocatalytic activity increased with decreasing ZIF-8 level which was attributed to the formation of heterojunctions due to partial coverage of TiO2 surface. The 1st order reaction rate constant of ZIF-8/Cu-TiO2 nanocomposite containing 5% ZIF-8 was found to be 4 and 1.4 times that of bare ZIF-8 and Cu-TiO2, respectively. Partial coverage of TiO2 surface with ZIF-8 crystals lead to the formation of light exposed ZIF-8/Cu-TiO2 heterojunction sites for the enhanced degradation of the dye molecule. The presence of ZIF-8 in the nanocomposite also increased the adsorption of the organic dye by the interaction with open Zn2+ metal sites of ZIF-8 on the nanocomposite surface. This study revealed that ZIF-8/Cu-TiO2 nanocomposites could be prepared at low ZIF-8 levels and short growth times with higher photocatalytic activities than their constituents and nanocomposites prepared at higher ZIF-8 levels and longer growth times.

Sonocrystallisation of ZIF-8 in water with high excess of ligand: Effects of frequency, power and sonication time

A systematic study on the sonocrystallisation of ZIF-8 (zeolitic imidazolate framework-8) in a water-based system was investigated under different mixing speeds, ultrasound frequencies, calorimetric powers and sonication time. Regardless of the synthesis technique, pure crystals of ZIF-8 with high BET (Brunauer, Emmett and Teller) specific surface area (SSA) can be obtained in water after only 5 s. Furthermore, 5 s sonication produced even smaller crystals (~0.08 µm). The type of technique applied for producing the ZIF-8 crystals did not have any significant impact on crystallinity, purity and yield. Crystal morphology and size were affected by the use of ultrasound and mixing, obtaining nanoparticles with a more spherical shape than in silent condition (no ultrasound and mixing). However, no specific trends were observed with varying frequency, calorimetric power and mixing speed. Ultrasound and mixing may have an effect on the nucleation step, causing the fast production of nucleation centres. Furthermore, the BET SSA increased with increasing mixing speed. With ultrasound, the BET SSA is between the values obtained under silent condition and with mixing. A competition between micromixing and shockwaves has been proposed when sonication is used for ZIF-8 production. The former increases the BET SSA, while the latter could be responsible for porosity damage, causing a decrease of the surface area.

An environmental-friendly pesticide-fertilizer combination fabricated by in-situ synthesis of ZIF-8

Stimulus-responsive pesticide or fertilizer systems have been emerged to improve the use efficiency of agrochemicals, reduce over-application and ensuing environmental problems. However, environmental-friendly synthesis of these systems still remain challenging. In this work, an environmental-friendly synthesis strategy has been developed to form a pesticide and fertilizer combination to achieve the integration of plant protection and nutrient supply. This pesticide-fertilizer combination system was fabricated using ammonium zinc phosphate (ZNP) and in-situ synthesized zeolitic imidazolate framework-8 (ZIF-8) as nutrients resources, and dinotefuran (DNF) as a pesticide. DNF was encapsulated in-situ (loading capacity of 12.32 ± 0.46%) during the ZIF-8 crystal synthesis process, rather than loaded by further adsorption, which improved its stability and prevented premature or rapid release. The hydrophobic ZIF-8 provided a pH-responsive slow-release behavior. The cumulative released DNF within seven days at pH 4.0, 7.0 and 10.0 was 66.30%, 40.41%, and 37.44%, respectively. The pesticide-fertilizer combination system showed significant effects on corn seed pre-cultivation, soil cultivation and pest control. This work provides a strategy for the integration of pesticide and fertilizer, which will reduce negative environmental effects caused by their over-applications and have great potential in modern sustainable agriculture.

In-situ growth of metal-organic frameworks in a reactive 3D printable material

The additive manufacturing (3D printing) of porous materials will open unprecedented opportunities to design advanced supports for extraction and separation. Here we have fabricated a reactive ZnO nanoparticle (NP)/thermoplastic composite filament for 3D printing via fused deposition modeling. The composite filament contains a 10 wt% ZnO-NPs incorporated in the thermoplastic acrylonitrile butadiene styrene (ABS). After 3D printing with the ZnO-NP/ABS filament, crystals of the zeolitic imidazolate framework-8 (ZIF-8) are grown in-situ on the 3D printed part. In-situ ZIF-8 crystallization is achieved by a mild chemical conversion mechanism at room temperature, converting the embedded ZnO nanoparticles into ZIF-8 crystals which are subsequently expressed on the surface of the 3D printed device. The resulting ZIF-8@ZnO-NP/ABS 3D printed devices were applied to the extraction of malachite green as a model water pollutant, and delivered superior performance compared with an identical device made of pure ABS, or the precursor ZnO-NP/ABS. For comparison purposes, a ZIF-8/ABS filament was fabricated with a 10 wt% load of presynthesized ZIF-8 crystals. The in-situ ZIF-8 growth approach again showed enhanced extraction performance in comparison with materials directly loaded with ZIF-8 crystals, with an increase of 48% in the extraction of malachite green. This is the first example of ZnO to ZIF-8 chemical conversion on 3D printed devices.

Development of MOF Reinforcement for Structural Stability and Toughness Enhancement of Biodegradable Bioinks.

Three-dimensional (3D) bioprinting is a technology that can precisely fabricate customized tissues and organs. Hydrogel materials that can embed living cells for use in 3D printing are called bioinks. However, there are only limited options of bioinks currently because they require the following features at once, such as printability, repetitive layer-by-layer stacking (stackability), structure stabilization, and biological properties. A polyurethane-gelatin double network hydrogel bioink was previously reported to own tunable modulus through changing the solid content, but cell viability at the high solid content is inevitably reduced. In the present study, the reinforcement effects of a metal-organic framework (MOF), zeolitic imidazolate framework-8 (ZIF-8), in the PUG bioink were evaluated. The printability, stackability, thermoresponsiveness, and shear-thinning behavior of the PUG-ZIF-8 composite hydrogels were examined. It was found that the PUG composite hydrogel containing 1250 μg/mL ZIF-8 crystals showed significant structural stability and modulus enhancement (∼2.5-fold). However, the PUG bioink containing 1250 μg/mL ZIF-8 crystals may lead to cell senescence or death. The cytocompatible concentration of ZIF-8 crystals in the bioink was about 875 μg/mL, and this concentration was much higher than the reported tolerable amount (∼50 μg/mL) of ZIF-8 for biomedical applications. The strong reinforcement effect of ZIF-8 and the drug-loading/sensing possibilities of MOFs may open new opportunities for using MOFs in 3D bioprinting applications.

Inclusion of zeolitic imidazolate framework-8 (ZIF-8) crystals within porous polyether sulfone (PES) via filtration methods as potential electrolytes for DMFC applications

The imidazolate framework-8 (ZIF-8) crystals were synthesized by in -situ growth techniques inside the pore of porous poly ether sulfone (PES) in order to fabricate a composite PES/ZIF-8 electrolyte membrane for direct methanol fuel cell (DMFC) applications. In situ techniques by adapting the filtration method was adhered in this study. It was found that the proton conductivity (17.9 × 10−3 Scm−1) was drastically increased for PES/ZIF-8 as compared to pristine PES membrane (0.21 × 10−3 Scm−1). However, the methanol barrier property was slightly decreased from 2.07 × 10−7 cm2s−1 to 3.88 × 10−7 cm2s−1 for PES and PES/ZIF-8 membranes, respectively. The introduction of ZIF-8 in PES membranes not only improve proton conductivity, but also positively affected the mechanical stability of PES/ZIF-8 with 1.73-fold lower of swelling ratio even though the water uptake increased by 2.08 folds. In spite of the increment in methanol permeability, selectivity of PES/ZIF-8 membrane was 6 folds and 2 folds higher than pristine PES and Nafion®, respectively which indicated that the potential for PES/ZIF-8 to be a good candidate for electrolyte in DMFC applications. Nonetheless, via scanning electron microscopy (SEM) showed a good distribution of ZIF-8 crystals inside the pore of PES membranes which proven that the effectiveness of filtration techniques for ZIF-8 crystals in-situ growth synthesized within the pores.