Zeolitic Imidazolate Framework Research Articles

Anchoring Metal-Nitrogen Sites on Porous Carbon Polyhedra with Highly Accessible Multichannels for Efficient Oxygen Reduction.

Transition metal-nitrogen-carbon complexes, featuring single metal atoms embedded in a nitrogen-doped carbon matrix, emerge as promising alternatives to traditional platinum-based catalysts, offering cost-effectiveness, abundance, and enhanced catalytic performance. This work introduces a novel method for the etching and doping of zeolitic imidazolate frameworks (ZIFs) with transition metals, creating a uniform distribution of secondary metal centers on ZIF surfaces. By disrupting the crystalline symmetry of ZIFs through synthetic defect engineering, we gain access to their entire internal volume, creating multichannel pathways. The absorption of metal ions is theoretically simulated, demonstrating their thermodynamically spontaneous nature. The selective removal of defect channels under Lewis acidic conditions, induced by metal ion alcoholysis/hydrolysis, facilitates the introduction of metal atoms into ZIF cavities. The resulting single-atom catalyst, after pyrolysis, features a three-dimensional (3D) multichannel structure, high surface area, and uniformly dispersed metal atoms within the N-doped carbon matrix, establishing it as an exceptional catalyst for the oxygen reduction reaction (ORR). Our findings highlight the potential of using metal etching in defect-engineered metal-organic frameworks (MOFs) for single-atom catalyst preparation, paving the way for the next generation of high-performance, cost-effective ORR catalysts in sustainable energy systems.

Study on the tribological behavior of TiN-VN/PAO composite lubricant system: ZIF-8 as a lubricating additive

Safety and reliability of mechanical systems are compromised by the lubricant degradation and excessive wear on contact surfaces. In response, a TiN-VN/PAO lubrication system was developed, and zeolitic imidazolate frameworks-8 (ZIF-8) nanoparticles with highly ordered pore structures were introduced to improve friction performance. The findings indicate that the addition of ZIF-8 significantly reduces the friction coefficient and wear rate in the composite system. The outstanding anti-friction performance is attributed to the heterogeneous TiN-VN nanolaminates material, which provides exceptional deformation tolerance and interface friction products. XPS analysis reveals the formation of a low shear strength Magnéli phases (V2O5) on the wear track surface, while TEM observations demonstrate that a ∼18 nm Zn-rich layer was developed at the interface, acting as a lubricating barrier layer.

PH and redox dual-responsive ZIF-8-based nanoplatform for targeted pathogens and environmental protection

Environmental stimulus-responsive controlled-release nanopesticides have the ability to adapt to the specific microenvironment of pathogen outbreaks, which can improve pesticide utilization efficiency. A pH and redox dual-stimuli responsively controlled release system (ZIF-8@Hex@Fe/GA) using zeolitic imidazolate framework-8 (ZIF-8) as the support and metal-phenol complex (Fe-GA) as the capping agent was constructed to deliver hexaconazole (Hex) for management of Phomopsis sp. The ZIF-8@Hex@Fe/GA composite demonstrated a high loading capacity and effectively improved the light stability of Hex. The hydroxyl groups present in the composite facilitate its diffusion on kiwifruit leaves, improving wettability. Additionally, the large specific surface area of ZIF-8@Hex@Fe/GA provides resilience against rainwater scouring. This innovative system intelligently responds to the acidic and oxidizing conditions associated with Phomopsis sp. infections, ensuring targeted and controlled release of Hex. Bioactivity assessments revealed that ZIF-8@Hex@Fe/GA exhibited protective effects of 84.16 ± 3.37 % and 80.77 ± 2.08 % on kiwifruit fruits and leaves at a concentration of 100 mg/L, outperforming Hex emulsifiable concentrate (Hex EC) by 21.34 % and 25.39 %, respectively. The acute toxicity of ZIF-8@Hex@Fe/GA to zebrafish was reduced 9-fold compared to Hex EC. Furthermore, ZIF-8@Hex@Fe/GA showed high safety for HEK293 cells, with a cell survival rate of 81.59 ± 2.11 % after 72 h of 10 mg/L treatment, whereas the cell survival rate for Hex TC, treatment was only 1.79 ± 1.32 % after 72 h. In conclusion, ZIF-8@Hex@Fe/GA demonstrates significant potential for targeted pesticide delivery and environmental protection.

Einblicke in die Mechanochemische Glasbildung von Zeolithischen Imidazolat‐Gerüstverbindungen

AbstractGläser von metallorganischen Gerüstverbindungen (MOF‐Gläser), die für ihr Potenzial bei der Gastrennung, in der Optik und als Festkörperelektrolyte bekannt sind, profitieren von der Verarbeitbarkeit ihres (unterkühlten) flüssigen Zustands. Traditionell werden MOF‐Gläser durch Erhitzen von MOF‐Kristallen über ihren Schmelzpunkt und anschließendes Abkühlen des flüssigen MOF auf Raumtemperatur unter einer inerten Atmosphäre hergestellt. Diese Technik des Schmelzquenchens ist zwar effektiv, erfordert aber aufgrund der hohen Temperaturen einen hohen Energieaufwand. Außerdem schränkt es den Spielraum für die Entwicklung neuer Materialien ein, da nur die thermisch hochstabilen Kombinationen von Metallionen und Linkern in Frage kommen. Eine Alternative, das mechanische Mahlen bei Raumtemperatur, hat sich als geeignet erwiesen, MOF‐Kristalle in amorphe Phasen umzuwandeln. Die spezifischen Bedingungen, unter denen diese amorphen Phasen ein glasähnliches Verhalten zeigen, sind jedoch noch nicht bekannt. In dieser Studie untersuchen wir die mechanochemische Amorphisierung und Verglasung einer Vielzahl von zeolithischen Imidazolat‐Gerüstverbindungen (ZIFs) mit verschiedenen Linkern und unterschiedlichen Metallionen (Zn2+, Co2+ und Cu2+) bei Raumtemperatur. Unsere Ergebnisse zeigen, dass ZIFs, die schmelzbar sind, durch Kugelmahlen erfolgreich in Gläser umgewandelt werden können. Bemerkenswerterweise können auch einige nicht schmelzbare ZIFs mit Hilfe der Kugelmahltechnik verglast werden, wie die Herstellung des ersten ZIF‐Glases mit Cu2+‐Ionen zeigt.

Microwave synthesis of composite of AgInS2 quantum dots and zeolitic imidazolate framework-8 for application in white light emitting diodes

Preparation of AgInS2 quantum dots (AIS QDs) with high photoluminescence quantum yield (PLQY) and thermal stability remains an important challenge. In this paper, AIS QDs were successfully introduced into zeolitic imidazolate framework-8 (ZIF-8) by microwave-assisted hydrothermal method. Due to the effective isolation of the ZIF-8, the AIS QDs avoid the concentration quenching when they were assembled into white light emitting diodes (WLEDs) devices as color conversion materials. More importantly, the generation of ZnS layer between the interfaces of AIS QDs and ZIF-8 can efficiently improve the optical performance of AIS QDs, resulting in the fluorescence lifetime extended to 470.05 ns. Meanwhile, the PLQY of AIS/ZIF-8 composite reached up 34.30 % when microwave hydrothermal heating at 120 °C for 60 min with AgIn/Zn=1/3, which was higher than that of the pristine AIS QDs as 25.30 %. Finally, the WLED devices were fabricated by combining AIS/ZIF-8 composite fluorescent powder with (Ba, Sr)Si2O2N2:Eu2+ phosphors and blue LED. At 20 mA, the AIS/ZIF-8 based WLED shows the luminous efficiency (LE) of 44.54 lm/W, correlated color temperature (CCT) of 4242 K and color rendering index (CRI) of 89.1. Moreover, the Commission International de L'Eclairage (CIE) was (0.36, 0.35), indicating the WLED emited warm white light. The present strategy aims at enhancing the optical performance of AIS QDs, which also may trigger the development of QDs-based WLED.

One-pot in situ synthesis of ZIF particles to prepare thin-film nanocomposite membranes for CO2 separation

Mixed matrix membranes (MMMs) are more likely to break the Robeson upper bound because they combine the pros of both organic and inorganic membranes. However, in the conventional MMM preparation processes, multi-steps are normally needed and, in many cases, the particle agglomeration and consequent non-selective voids are unavoidable, resulting in poor carbon dioxide (CO2) separation performances. In addition, the agglomeration makes it challenging to fabricate thin-film nanocomposite (TFN) membranes. In this study, zeolitic imidazolate framework (ZIF)-8- and ZIF-67-based TFN membranes were fabricated via a facile one-pot in situ synthesis protocol. The ZIF particles were synthesized in the polymeric solution, then the TFN membranes were fabricated by a dip coating method. With a casting solution concentration of 1.5 wt.%, a selective layer with a thickness of ∼300 nm can be prepared on the porous polyacrylonitrile (PAN) support. The results of thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), Fourier Transform Infrared (FT-IR) spectroscopy, and X-ray diffraction (XRD) showed that ZIFs were successfully synthesized in the casting solution. At 35 °C and 2 bar, the membrane containing 5 wt.% ZIF-67 had a CO2 permeance of 223.35 gas permeation unit (GPU), which was 16.55 % higher than that of pure Pebax.

Template Role of Long Alkyl-Chain Amides in the Synthesis of Zeolitic Imidazolate Frameworks.

Organic amides as solvents and structure directing agents (SDAs) are crucial for synthesizing zeolitic imidazolate frameworks (ZIFs). However, current research focuses only on the use of short alkyl-chain amides as solvents/SDAs. Here, we investigate the role of amides with varying alkyl-chain lengths on the structures and topologies of Zn(Im)2 polymorphs. Using short alkyl-chain amides as solvents, the Zn(Im)2 topological structures are affected by the synthesis conditions, leading to "one SDA/multiple topological structures". In contrast, when long alkyl-chain amides are used as solvents, the Zn(Im)2 topological structures are essentially unaffected by other synthesis conditions. Thus, long alkyl-chain amides are shown for the first time to exhibit a significant template role, leading to "one template/one topological structure". Specifically, the use of long alkyl-chain N,N-dimethyl-Cn amides (abbreviated as DM-Cn amides, n = 3, 4, 6, 8, and 10) can lead to only DTF-type Zn(Im)2 frameworks under broad crystallization conditions. Single-crystal X-ray diffraction confirmed that the exquisite structural compatibility between long alkyl-chain DM-Cn amides and the DFT-type Zn(Im)2 framework results in a highly regular head-to-tail arrangement of amides along the (kaa-lov) n chain of the DFT framework. The template role for long alkyl-chain amides was further identified to be multiple C-H···π interactions between DM-Cn amides and Zn(Im)2 frameworks thanks to molecular simulations.

Zeolitic imidazolate framework derived stellate shaped cobalt-molybdenum hybrid sulfide microflower for enhanced supercapacitor properties

Zeolitic imidazolate frameworks (ZIFs) represent a class of material exhibiting a well-defined geometry. The ZIF derivatives are known to inherit the parent morphology and have emerged as a potential platform for developing superior electrode materials. In this study, leaf-like ZIF-67 is synthesized using a chemical route and employed as the sacrificial template in one-pot hydrothermal sulfurization for preparing Co3S4-Mo15S19, cobalt‑molybdenum hybrid sulfide (CMS/NF). The unique stellate-shaped architecture of the CMS/NF microflowers enhances the exposure of the redox active sites, improving charge storage and exhibiting superior performance. On account of the synergy of the metal ions and stellate-shaped hierarchical architecture, the CMS/NF hybrid sulfide shows an excellent specific capacitance value of 3283 F g−1 at a current density of 1 A g−1 with capacitance retention of 77.7 % at 10 A g−1. An asymmetric supercapacitor device based on CMS/NF hybrid sulfide with aqueous KOH electrolyte exhibits a high specific energy of 40.8 Wh kg−1 at 400 W kg−1 with excellent cycling life of 81 % after 5000 cycles with ∼100 % coulombic efficiency. In addition, the density functional theory-based simulations have been carried out for the Co3S4-Mo15S19 hybrid system to develop a better understanding. From the total density of states, it is concluded that compared to the pristine structures, the hybrid system has enhanced states close to the Fermi level, confirming the conductivity improvement. Computed quantum capacitance for the pristine and hybrid systems corroborates the experimental capacitance consequences. Hence, the theoretical examinations warrant our electrochemical results and provide insight into developing high-performance supercapacitor electrodes.

Machine Learning Optimizing Enzyme/ZIF Biocomposites for Enhanced Encapsulation Efficiency and Bioactivity.

In this study, we present the first example of using a machine learning (ML)-assisted design strategy to optimize the synthesis formulation of enzyme/ZIFs (zeolitic imidazolate framework) for enhanced performance. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were chosen as model enzymes, while Zn(eIM)2 (eIM = 2-ethylimidazolate) was selected as the model ZIF to test our ML-assisted workflow paradigm. Through an iterative ML-driven training-design-synthesis-measurement workflow, we efficiently discovered GOx/ZIF (G151) and HRP/ZIF (H150) with their overall performance index (OPI) values (OPI represents the product of encapsulation efficiency (E in %), retained enzymatic activity (A in %), and thermal stability (T in %)) at least 1.3 times higher than those in systematic seed data studies. Furthermore, advanced statistical methods derived from the trained random forest model qualitatively and quantitatively reveal the relationship among synthesis, structure, and performance in the enzyme/ZIF system, offering valuable guidance for future studies on enzyme/ZIFs. Overall, our proposed ML-assisted design strategy holds promise for accelerating the development of enzyme/ZIFs and other enzyme immobilization systems for biocatalysis applications and beyond, including drug delivery and sensing, among others.

Modulating N doping in cobalt-derived catalyst from zeolitic imidazolate frameworks for high performance zinc-air batteries

In this work, the N-content was varied using ammonium hydroxide (A), urea (U), and melamine (M) impregnated in a zeolitic imidazolate framework (ZIF-67) with a Co to Zn ratio of 7:93. The N-doped ZIF-derived carbon materials and the reference ZIF Co 7:93 underwent pyrolysis under identical conditions, yielding C-ZIF, CA-ZIF, CU-ZIF, and CM-ZIF. Different nitrogen sources mainly affected the surface area and graphitic-N content, yielding up to three times the N-content of the reference. All materials presented ORR onset potentials near 0.9 V and E10mA cm−2 near 1.6 V for the OER. However, CM-ZIF enabled rechargeability at different current densities, with a round-trip efficiency of 68.8 % at 5 mA cm−2, decreasing only to 54 % at 15 mA cm−2.

Combining Protein Phase Separation and Bio-orthogonal Linking to Coimmobilize Enzymes for Cascade Biocatalysis.

The designed and ordered co-immobilization of multiple enzymes for vectorial biocatalysis is challenging. Here, a combination of protein phase separation and bioorthogonal linking is used to generate a zeolitic imidazole framework (ZIF-8) containing co-immobilized enzymes. Zn2+ ions induce the clustering of minimal protein modules, such as 6-His tag, proline-rich motif (PRM) and SRC homology 3 (SH3) domains, and allow for phase separation of the coupled aldoketoreductase (AKR) and alcohol dehydrogenase (ADH) at low concentrations. This is achieved by fusing SpyCatcher and PRM-SH3-6His peptide fragments to the C and N termini of AKR, respectively, and the SpyTag to ADH. Addition of 2-methylimidazole results in droplet formation and enables in situ spatial embedding the recombinant AKR and ADH to generate the cascade biocalysis system encapsulated in ZIF-8 (AAE@ZIF). In synthesizing (S)-1-(2-chlorophenyl) ethanol, ater 6 cycles, the yield can still reach 91%, with 99.99% enantiomeric excess (ee) value for each cycle. However, the yield could only reach 72.9% when traditionally encapsulated AKR and ADH in ZIF-8 are used. Thus, this work demonstrates that a combination of protein phase separation and bio-orthogonal linking enables the in situ creation of a stable and spatially organized bi-enzyme system with enhanced channeling effects in ZIF-8.

Illuminating the fight against breast cancer: Preparation and visualized photothermal therapy of hyaluronic acid coated ZIF-8 loading with indocyanine green and cryptotanshinone for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is characterized by higher recurrence rate and mortality. Thermally-mediated ablation via photothermal therapy (PTT) demonstrates considerable promise for the eradication of breast cancer. Nonetheless, the efficacy of PTT is impeded by the thermal tolerance of tumor cells, which is attributed to the augmented expression of heat shock proteins (HSPs). These proteins, which function as ATP-dependent molecular chaperones, confer protection to cancer cells against the cytotoxic heat generated during PTT. Glycolysis is an important way for breast cancer cells to produce ATP, which can promote the occurrence and development of lung metastasis of breast cancer. Therefore, inhibiting glycolysis may diminish the expression of HSPs, curtail the growth of breast cancer, and prevent its metastasis. Glycolytic metabolism plays a pivotal role in the ATP biosynthesis within breast cancer cells, facilitating the progression and dissemination of pulmonary metastases. Consequently, targeting glycolysis presents a strategic approach to HSP expression, the proliferation of breast cancer, and impede its metastatic spread. Herein, we designed an indocyanine green (ICG) and cryptotanshinone (CTS) loaded hyaluronic acid (HA) coated Zeolitic Imidazolate Framework-8 (ZIF-8) drug delivery system. The drug delivery system had excellent photothermal properties, which could reach temperature sufficient for photothermal ablation of tumor cells. (ICG + CTS)@HA-ZIF-8 also showed pH-responsive drug release, enhancing the sustained release of ICG and CTS to extend their systemic circulation duration. Moreover, the HA modification of ZIF-8 served to augment its targeting capabilities both in vitro and in vivo, leveraging the enhanced permeation and retention (EPR) effect, as well as active tumor targeting via the CD44 receptor pathway, resulting in a higher drug concentration and a better therapeutic effect in tumor. (ICG + CTS)@HA-ZIF-8 could downregulate the expression of glycolysis-related protein pyruvate kinase-M2 (PKM2), thereby inhibiting the glycolysis process, further suppressing tumor cell energy metabolism, downregulating the expression of HSPs, overcoming tumor cell heat resistance, and improving PTT effect. It exhibited a notable suppressive impact on both the proliferation and migration of breast cancer cells, potentially offering innovative insights for the visualized PTT in breast cancer treatment.

Efficient photocatalytic degradation of malachite green dye from wastewater using facilely synthesized ternary ZIF-8/Ag/Ag2S nanocomposite: Optimization by RSM (CCD)

The current study compares the photocatalytic potential of zeolitic imidazolate framework-8 (ZIF-8) with ZIF-8 nanocomposites doped with two forms of silver (referred to as AgNPs/ZIF-8 and AgNPs/Ag2S/ZIF-8). Their physicochemical characteristics were evaluated using Fourier-transform infrared, X-ray diffraction, energy-dispersive X-ray, Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), diffuse reflectance spectroscopy (DRS), photoluminescence (PL), photocurrent density, Mott-Schottky, and Brunauer Emmett Teller techniques. The photocatalytic activity of the composites was assessed for degradation of malachite green (MG) under visible light irradiation in a solar-based staircase photoreactor for the first time. The optimization of the photodegradation process was achieved by employing central composite design, 0.020 g of AgNPs/ZIF-8 and ZIF-8photocatalyst (in 20 ml of solution), MG Concentration of 7 mg/l, pH of 8, and the irradiation time of 50 min. The predicted model had R2 and R2adj correlation coefficients of 0.987 and 0.975 respectively, which showed experimental results were very close to the predicted values. The results indicated remarkable efficiency in both degradation and mineralization, achieving the degradation rate of up to 98.6 %, a high-rate constant value of 0.0701 min-¹, and an 80 % mineralization efficiency. AgNPs/Ag2S/ZIF-8 exhibited superior photocatalytic performance in comparison to both AgNPs/ZIF-8 and ZIF-8. Different scavengers were used in the experiment and demonstrated that O2− played a crucial role in the photodegradation of MG. Moreover, the nanocomposite AgNPs/Ag2S/ZIF-8 exhibited robust stability and could be repeatedly utilized up to five cycles without notable decline in efficacy, rendering it an environmentally sustainable photocatalyst with promising prospects for industrial utilization.

Copper-loaded ZIF-8-based immunosensor for early diagnosis of chronic kidney disease by detecting neutrophil gelatinase-associated lipocalin (NGAL) biomarker

Metal-organic frameworks (MOFs) is a promising contender among the nanomaterials for biosensors due to their special properties, including high surface area, tunable porosity, and adaptable functionalization competences. Zeolitic imidazolate frameworks (ZIFs), a subclass of MOFs, have drawn precise attention for their excellent chemical stability and ease of synthesis. This study, for the first time, concentrates on the preparation and characterization of a Cu-loaded ZIF-8-based immunosensor for the detection of neutrophil gelatinase-associated lipocalin (NGAL), a crucial biomarker for chronic kidney disease (CKD). Loading copper (Cu) into the ZIF-8 framework improves its electrochemical properties, conductivity, and surface area, leading it an ideal platform for antibody immobilization and NGAL detection. The immunosensor utilized Staphylococcal Protein A (SPA) IgG binding protein for antibody immobilization, providing an alternative to traditional crosslinking chemistry, enhancing biosensor functionality. Structural analysis, morphological assessment, elemental mapping, and stoichiometric analysis confirmed the successful synthesis of Cu-loaded ZIF-8 nanocomposite. Assessment of the electrochemical performance of the immunosensor demonstrated sufficiently low limit of detection (80 pg mL−1) over a wide range of 0.1 ng mL−1 to 1000 ng mL−1 of NGAL along with superior selectivity, reproducibility, stability, and clinical feasibility. This advancement contributes to the rising knowledge on MOF-based biosensors and holds promise for future applications in disease diagnosis and healthcare monitoring.

Portable smartphone-assisted amperometric immunosensor based on CoCe-layered double hydroxide for rapidly immunosensing erythromycin

Herein, we have manufactured a newly designed bifunctional impedimetric and amperometric immunosensor for rapidly detecting erythromycin (ERY) in complicated environments and food stuffs. For this, bimetallic cobalt/cerium-layered double hydroxide nanosheets (CoCe-LDH NSs), which was derived from Co-based zeolite imidazole framework via the structure conversion, was simultaneously utilized as the bioplatform for anchoring the ERY-targeted antibody and for modifying the gold and screen printed electrode. Basic characterizations revealed that CoCe-LDH NSs was composed of mixed metal valences, enrich redox, and abundant oxygen vacancies, facilitating the adhesion on the electrode, the antibody adsorption, and the electron transfers. The manufactured impedimetric and amperometric immunosensor based on CoCe-LDH has showed the comparable sensing performance, having a wide linear detection range from 1.0 fg mL−1 to 1.0 ng mL−1 with the ultralow detection limit toward ERY. Also, the portable, visualized, and efficient analysis of ERY was then attained at the smartphone-assisted CoCe-LDH-based SPE.

Impact of Exposed Crystal Facets on Oxygen Reduction Reaction Activity in Zeolitic Imidazole Frameworks

Oxygen reduction reactions (ORR) are critical reactions for efficient sustainable and renewable energy storage. However, the limitation of ORR is a slow kinetic reaction due to the multi-step transfer mechanism of electrons. Therefore, electrocatalysts with high ORR activity and stability are needed to overcome the reaction limitations. Zeolitic imidazole framework-67 (ZIF-67) has attracted attention in electrochemical applications due to its multiple redox-active sites and high stability in alkali conditions. The Co-doped porous carbon catalysts derived from ZIF-67 have the potential to be used as ORR catalysts with high performance, while pure phase ZIF-67 electrocatalyst for ORR is rarely studied. The work studies the importance of crystal facets on ORR reactivity. The results show that ZIF-67 nanocube exhibits excellent ORR activity with lower half wave-potential and faster kinetics process compared to its bulk structure. It is proposed that ZIF-67 nanocube provides improvement of selectivity for the four-electron pathway, which is a favorable process with higher reaction efficiency. The density functional theory (DFT) calculations suggest unsaturated Co2+ active sites with enriched (100) facets in the cubic crystal. Therefore, the fast diffusion of oxygen molecules to active sites and strong interaction with intermediate are observed in a cubic structure. The correspondence between experiment and calculation offers enhancement of ORR activity and selectivity from control-specific growth of (100) facet with cubic shape. The work introduces a new strategy for designing highly efficient ORR electrocatalysts with facet-controlled, allowing further study in other electrochemical reactions.

Highly Dispersed Pd@ZIF-8 for Photo-Assisted Cross-Couplings and CO2 to Methanol: Activity and Selectivity Insights.

Our study unveils a pioneering methodology that effectively distributes Pd species within a zeolitic imidazolate framework-8 (ZIF-8). We demonstrate that Pd can be encapsulated within ZIF-8 as atomically dispersed Pd species that function as an excited-state transition metal catalyst for promoting carbon-carbon (C-C) cross-couplings at room temperature using visible light as the driving force. Furthermore, the same material can be reduced at 250 °C, forming Pd metal nanoparticles encapsulated in ZIF-8. This catalyst shows high rates and selectivity for carbon dioxide hydrogenation to methanol under industrially relevant conditions (250 °C, 50 bar): 7.46 molmethanol molmetal-1 h-1 and >99%. Our results demonstrate the correlations of the catalyst structure with the performances at experimental and theoretical levels.

Carboxylate-Based Metal-Organic Framework and Coordination Polymer Glasses: Progress and Perspectives.

ConspectusCoordination polymers (CPs) and metal-organic frameworks (MOFs) represent versatile materials with diverse structural and functional properties, making them appealing for various applications. However, their conventional forms, which are typically synthesized as powders or crystals, pose challenges due to limited processability and mechanical fragility. Recently, CP/MOF glasses have emerged as promising alternatives, offering enhanced processability while retaining some of the unique characteristics shown in the mother crystalline materials. Despite the prevalence of carboxylate ligands in CP/MOF synthesis, the development of carboxylate-based CP/MOF glasses has been limited compared to that of zeolitic-imidazole framework (ZIF)-based glasses. This is attributed to the strong metal-ligand bonds and low thermal stability of carboxylic acids, which hinder their melting in CP/MOF structures. Nonetheless, recent advancements have led to a surge in methods for synthesizing carboxylate-based CP/MOF glasses. So far, desolvation and melt-quenching have been introduced for achieving glass structures from CP/MOF precursors.The first melt-quenched MOF glass was reported in 2015 with ZIFs. However, we informally observed the melting of the MOF during thermal decomposition research of aliphatic carboxylate-based MOFs as a sacrificial template dating back to 2013. In that study, aliphatic ligands, instead of aromatic carboxylate, were employed due to their high lability, lower thermal stability, and high degree of freedom, which facilitated pyrolysis. The results were published with a focus on synthesizing hierarchically porous MgO via the pyrolysis of an aliphatic ligand-based Mg-MOF in an inert environment. A decade later, it was revisited and studied as the first melt-quenched carboxylate-based MOF glass, converted from a crystalline MOF through the liquid phase before decomposition during the heating process.This Account aims to introduce six studies, including the aforementioned example, on the synthesis of CP/MOF glasses from carboxylate-based CPs/MOFs that have been published so far. To overcome the challenges with aromatic carboxylates in CP/MOF glass formation, the metal coordination sphere should be altered and the degree of freedom in the ligands should be increased. Based on these approaches, the strategies for vitrification of carboxylate-based CPs/MOFs can be divided into two categories: desolvation and melt-quenching. Desolvation can be preceded by vapor perturbation such as hydration. Carboxylate-based CP/MOF glasses possess the potential to expand into a broader range of applications beyond those of existing CP/MOF glasses. Alongside the diversity offered by carboxylic acid ligands, these materials mirror the extensive range of applications previously explored in the existing carboxylate-based CP/MOF crystals. Moreover, their high processability, inherent to glass materials, enables their applications in various industrial fields. This versatility may extend to previously unexplored areas of utilization such as a novel class of bioactive glass.

(Digital Presentation) In-Situ Growth of CNT and Macroporous ZIF on Bacterial Cellulose for High Frequency Electrochemical Capacitor

High frequency electrochemical capacitors (HF-ECs) represent a class of devices characterized by their high capacitive density and operational capability within the hundreds or kilohertz range. As electronic devices continue to undergo downsizing trends, HF-ECs emerge as promising alternatives to bulky aluminum electrolytic capacitors (AECs), which are constrained by their limited working frequency of approximately 1 Hz and slow charge-discharge rates. The designing of electrodes of HF-ECs combines large surface area for capacitive density along with open porous network to facilitate rapid ion transport. In this study, we synthesized nickel coordinated ZIF-8 (Zeolitic Imidazole Framework-8) cages on bacterial cellulose (BC). The samples underwent rapid carbonization in the presence of dicyandiamide at ~950˚C for 20 minutes, during which the zinc centers inside the MOF cages evaporated forming macroporous structures, while the nickel particles gave rise to carbon nanotube (CNT) growth through tip growth mechanism. The uniform coverage of BC with macroporous ZIF cages reduces the microporous effect, while the CNT growth also imparts higher electronic conductivity via graphitic nitrogen groups. The HF-ECs made with these electrodes and 6M KOH aqueous electrolyte gave a capacitive density of ~3.4 mFcm-2 and a phase angle of -81.3˚. The electrodes were stacked in pairs of 2 and 3 to achieve higher capacitance of 6.3 mFcm-2 and 8.9 mFcm-2 respectively. The HF-ECs were also assembled with 1 M TEABF4 in acetonitrile to show higher working voltage of these electrodes. The device maintained a capacitance just above 3 mFcm-2 and a phase angle over -80˚. The cells show an excellent working capability at higher discharge rates of 100 mAcm-2, where they retained ~70% of the initial capacitance. Figure 1

MOF-Supported Intermetallic Pt-Ni Electrocatalyst for the Oxygen Reduction Reaction

The catalyst support materials demonstrate great influence on the performance and durability of oxygen reduction reaction (ORR) electrocatalysts. Metal organic frameworks (MOFs) have been the focus of many Pt alloyed catalyst supports due to their large surface areas and well-defined pore structures. MOF-based carbon supports and a special class of MOFs that have a zeolite-type structure, and Zeolitic imidazolate frameworks (ZIFs) offer high ORR activity and enhanced stability of Pt-alloyed catalysts due to their porous structure, large surface area, and good electrical conductivity. In this study, we used two different MOF-based supports, Mn-NC and ZIF-67 derived Co-NC, to synthesize a nitrogen (N)-doped intermetallic PtNi catalyst. The synthesized material exhibits enhanced ORR activity and stability in an acidic electrolyte that is superior to commercial Pt/C catalyst. The rotating disk electrode (RDE) measurements of the PtNi/Co-NC catalyst demonstrated that the mass activity (MA) and specific activity (SA) are 0.9 A mgPt -1 and 1.8 mA cm-2, respectively at 0.9 V. The synthesized PtNi/Mn-NC catalyst demonstrated 1.4 A mgPt -1 and 2.1 mA cm-2 at 0.9 V, which are higher than those achieved with the commercial Pt/C. The MEA performance of the MOF-based PtNi catalysts will also be discussed. The mechanism of the enhanced performance of the catalysts is being formulated, based on in situ X-ray absorption spectroscopy (XAS) analysis. This work provides a promising approach to improve the activity and stability of binary and ternary Pt-based electrocatalysts for ORR by the use of MOF-based supports.