Bimetallic Zeolitic Imidazolate Framework Research Articles

The glass transition in the high-density amorphous Zn/Co-ZIF-4.

The high-density amorphous phases (HDAs) of bimetallic zeolitic imidazolate frameworks (Zn/Co-ZIF-4) were prepared. The temperature dependence of the isobaric heat capacity (Cp) of ZIF-4 HDAs was measured to determine the glass transition temperature (Tg) of HDAs. The Tg non-linearly decreases with the molar ratio R, where R is Co/(Co + Zn), indicating the presence of a mixed-metal node effect. This effect arises from the non-linear increase of the degree of configurational freedom in the HDA as R increases. The degree of configurational freedom is inversely correlated with the network connectivity, which is, in turn, affected by variations in the MN4 (M: Zn or Co; N: nitrogen) tetrahedral symmetry in the ZIF-4 HDA. Overall, this work offers valuable insights into the glass transition of metal-organic frameworks.

Zeolitic Imidazolate Framework Decorated Molybdenum Carbide Catalysts for Hydrodeoxygenation of Guaiacol to Phenol

Bimetallic zeolitic imidazolate framework (BMZIF)-decorated Mo carbide catalysts were designed for the catalytic hydrodeoxygenation of guaiacol to produce phenol with high selectivity. A uniform layer of BMZIF was systematically coated onto the surface of the MoO3 nanorods. During carbonization at 700 °C for 4 h, BMZIF generated active species (ZnO, CoO) on highly dispersed N-doped carbons, creating a porous shell structure. Simultaneously, the MoO3 nanorod was transformed into the Mo2C phase. The resulting core@shell type Mo2C@BMZIF-700 °C (4 h) catalyst promoted a 97% guaiacol conversion and 70% phenol selectivity under 4 MPa of H2 at 330 °C for 4 h, which was not achieved by other supported catalysts. The catalyst also showed excellent selective cleavage of the methoxy group of lignin derivatives (syringol and vanillin), which makes it suitable for selective demethoxylation in future biomass catalysis. Moreover, it exhibits excellent recyclability and stability without changing the structure or active species.

One-dimensional hierarchical ZnCo-NCNT/Mo2C nanostructure as a high-efficiency bifunctional catalyst for rechargeable Zn-air batteries

Herein, a catalyst precursor is prepared by depositing bimetallic zeolitic imidazolate frameworks (BMZIFs) on a polypyrrole (PPy)-coated MoO3 nanobelt (NB). Next, BMZIFs (ZIF-8/ZIF-67), PPy and MoO3 are calcined into Co nanoparticles (NPs) dotted/Zn, Co doped carbon, nitrogen doped carbon nanotube (NCNT) and Mo2C NPs at 800 °C, respectively, to produce a one-dimensional (1D) hierarchical nano-catalyst. The 1D nano-catalyst with porous surface, large specific area and abundant defects maximumly exposes the catalytic active sites. Furthermore, the entire encapsulation of Mo2C NPs by NCNTs effectively restrains their agglomeration during the pyrolysis, and volume change in electrochemical reaction. Moreover, the simultaneous immobilization of bimetallic ZIFs on PPy is more likely to form small-sized Zn/Co NPs on NCNT than single ZIF. Accordingly, the nano-catalyst exhibits a small ΔE value of 0.791 V and the Zn-air battery based on this catalyst achieves an excellent peak power density of 231.6 mW cm−2 at 5 mA cm−2, and a much higher energy round-trip efficiency than Pt/C + RuO2 in the long-term (400 h) cycling experiment. The excellent ORR/OER behaviors of the catalyst is mainly attributed to the synergy between CoN4-graphene and Mo2C, which is verified by both experimental and density function theory (DFT) calculation results.

In-situ fabrication of bio-inspired nanocatalysts for enhanced oxygen reduction reaction in alkaline media

Designing a fuel cell based on non-precious metal-based electrocatalysts with high reduction potential and stability against methanol/carbon monoxide (MeOH/CO) poisoning is quite challenging. Taking inspiration from naturally occurring enzymes, materials with earth-abundant metal centers embedded in organic framework helps to expedite the kinetics of the oxygen reduction reaction (ORR) by providing more O2 adsorption sites through positively charged N atoms. Thus, herein, we have fabricated novel bioinspired nitrodopamine derived (NDA) N rich C coated bimetallic zeolitic imidazolate framework (NDA@BM-ZIF) through in-situ solvothermal synthesis approach. NDA@BM-ZIF based electrode offers high half wave potential value (E1/2 = 0.915 V) and high tolerance against MeOH poisoning (91.4%) even better than dopamine (DA) derived NC coated BM-ZIF (86.1%) and commercially available Pt/C (87.3%). The remarkable electrocatalytic efficacy of NDA@BM-ZIF could be ascribed to surface compatibility by providing positively charged O2 adsorption sites, increased surface defects and promote heterolytic O–O bond cleavage rather than homolytic cleavage thus resulting in fast electron transportation capability.

Capacity determination of ZnCo0.26O1.63–N0.18C0.82 derived from bimetallic zeolitic imidazolate framework as anode in sodium-ion battery

Capacity determination of ZnCo0.26O1.63–N0.18C0.82 derived from bimetallic zeolitic imidazolate framework as anode in sodium-ion battery

Bioinspired NC Coated BM‐ZIF for Electrochemical Monitoring of Adrenaline from Blood and Pharmaceutical Samples

AbstractHerein, we have developed highly sensitive and selective non‐enzymatic bioinspired polydopamine derived nitrogen rich carbon (NC) coated bimetallic zeolitic imidazolate framework (BM‐ZIF) electrochemical sensor via simple hydrothermal approach for monitoring adrenaline (AD) from COVID‐19 quarantined person blood and pharmaceutical sample. The designed NC‐BM‐ZIF electrode shows excellent sensitive and selective performance towards AD monitoring with detection limit (LOD) of 0.01 nM and 0.1931 μA/nM/cm2 sensitivity over a wide linear range of 50–1625 nM. To the best of our knowledge, this is the first study of using of NC‐BM‐ZIF electrode for the electrochemical sensing of AD from quarantined person blood and pharmaceutical sample.

Boosting wastewater bioelectricity recovery via solvent mediation and zinc fencing: Dual regulation for catalyst spatial structure and active sites

Bioelectrochemical systems (BESs) are promising in self-sustaining energy recovery of wastewater. Cathode catalysts are crucial to enhancing the oxygen reduction reaction (ORR) process in BESs. In this study, a dual regulation strategy including solvent mediation and zinc fencing was proposed for regulation of catalyst spatial structure and active sites. The particle size of catalysts derived from bimetallic zeolitic imidazolate frameworks (ZIFs) was tuned over a wide range via solvent mediation while the dispersion of cobalt active sites was achieved via zinc fencing. As-optimized cobalt active sites embedded nitrogen-doped porous carbon with a Co/Zn molar ratio of 1/20 (Co1/20@NPC) directed a four-electron transfer pathway in ORR process. The BES employing Co1/20@NPC as cathode catalyst produced a maximum power density of 2057 ± 21 mW m−2, 40% higher than the BES using Pt/C as cathode catalyst. Co1/20@NPC BES displayed fast organic elimination and efficient energy recovery with a coulombic efficiency of 73 ± 1% and a normalized energy recovery of 0.361 ± 0.006 kWh m−3. The outstanding ORR activity, high bioelectricity generation and operation stability made Co1/20@NPC a prospective cathode catalyst. This dual regulation strategy provides implications for controllable synthesis of ZIF-derived catalysts with tailored structures and characteristics, and demonstrates potential in improving wastewater energy recovery performance in BESs.

Metal–Organic Framework‐Derived Ultrafine ZnO/Co3ZnC Particles Embedded in N‐Doped Carbon Concave‐Dodecahedron Towards Enhanced Lithium Storage

AbstractTransition metal oxides (TMOs) are potential anode materials for lithium‐ion batteries (LIBs) owing to their superior theoretical capacities, environmental benignity and abundant supply. However, because of the intrinsically poor conductivity, inevitable volume variation, inferior capacity and cyclic stability, the progress of TMOs in practical application is seriously hindered. In this study, a new N‐doped carbon concave‐dodecahedron has been successfully manufactured through a facile method utilizing bimetallic zeolitic imidazolate framework (ZnCo‐ZIF) as both precursor and sacrificial template, in which ultrafine ZnO/Co3ZnC nanoparticles uniformly distributed on the surface can provide additional active sites to effectively accelerate the diffusion of lithium ions. As a result, the as‐prepared ZnO/Co3ZnC/C (ZCC) anode exhibits outstanding mechanical tolerance during lithiation process. Attributed to the superior structure and compositional optimization, the ZCC anode achieves remarkable electrochemical performance with considerable high‐rate capacity (424 mAh g−1 at 2.0 A g−1) and ultralong cyclability (942 mAh g−1 at 0.2 A g−1 after 300 cycles).

Heterointerface engineering of water stable ZIF-8@ZIF-67: Adsorption of rhodamine B from water

Elimination of toxic dye, one of the utmost and usual industrial pollution released in the natural water, is the very serious issue for the modern civilization. In this study, a novel bimetallic (ZIF-8@ZIF-67) zeolitic imidazolate frameworks (ZIFs) have been fabricated by a simple and straight forward technique at room temperature. Sodalite (SOD) cage type structure, morphology and porosity of synthesized bimetallic metal-organic frameworks (MOFs) were characterized by SEM, TEM, XRD and BET. The results of characterizations showed that the ZIF-8@ZIF-67 owns greater nano crystallinity, surface area and porosity. As compared to single metallic MOFs (ZIF-67 and ZIF-8), the physical and chemical properties of ZIF-8@ZIF-67 were improved. Accordingly, the ZIF-8@ZIF-67 potentially analysed for the exclusion of rhodamine B from water and the gained outcomes were compared with the efficiency of mono-metallic MOFs (ZIF-67 and ZIF-8). Several parameters, including initial dye concentrations, sonication time, and pH on dye removal efficiency were investigated. Additionally, Langmuir, Freundlich, Tempkin and Dubinin-Radushkevich isotherm models were used to explain the process of adsorption onto the surface of MOFs. The results disclosed that the Langmuir model sufficiently explained the adsorption procedure as monolayer with higher R2 values (R2 = 0.9924, 0.9822 and 0.9909 of ZIF-67, ZIF-8 and ZIF-8@ZIF-67 respectively). The mean free energy (E) was observed to be 0.551, 0.576 and 0.532 KJ.mol−1 for ZIF-67, ZIF-8 and ZIF-8@ZIF-67, respectively, exposing that the chemisorption dominates the process of adsorption. The qmax premeditated with Langmuir model was comparatively high (143.26 mg.g−1) as compared to ZIF-8 (56.40 mg.g−1) and ZIF-67 (81.63 mg.g−1), accrediting to the intensification in active binding sites. Further, the reusability of bimetallic MOFs was tested for four regeneration cycles and results were outstanding with only 8 ±1% decrease in efficiency. It is assumed that, the fabricated ZIF-8@ZIF-67 composite have high applicability for the adsorption of toxic dyes from water.

Zn–Co Bimetallic Zeolitic Imidazolate Frameworks as Nonenzymatic Electrochemical Glucose Sensors with Enhanced Sensitivity and Chemical Stability

Zn–Co Bimetallic Zeolitic Imidazolate Frameworks as Nonenzymatic Electrochemical Glucose Sensors with Enhanced Sensitivity and Chemical Stability

Cascade scaffold of porous carbon-coated carbon derivates from a bimetallic zeolitic imidazolate framework for use as an efficient sulfur host in high-performance Li-S batteries

Currently, there is increasing concern about meeting energy demands, and a lithium-sulfur (Li-S) battery is a promising candidate for use in next-generation energy storage systems. However, some problems still limit the practical implementation of Li-S batteries. Herein, we present a conductive cascade scaffold developed by depositing a porous carbon over a nanoporous carbon layer derived from bimetallic zeolitic imidazolate (BMZIF) as an efficient sulfur host for use in Li-S batteries. Due to the increased conductivity, abundant active sites and large surface area of this prepared material, the assembled Li-S batterie exhibits excellent rate and long cycling performances. Results show an outstanding reversible cycling capacity above 1004.1 mAh/g at 0.2 C for over 100 cycles. This work is designed to effectively address the problems of sulfur electrodes and proposes a new scheme of hosting sulfur in Li-S batteries.

Nanoarchitectonics of the cathode to improve the reversibility of Li-O2 batteries.

The strategic design of the cathode is a critical feature for high-performance and long-lasting reversibility of an energy storage system. In particular, the round-trip efficiency and cycling performance of nonaqueous lithium–oxygen batteries are governed by minimizing the discharge products, such as Li2O and Li2O2. Recently, a metal–organic framework has been directly pyrolyzed into a carbon frame with controllable pore volume and size. Furthermore, selective metallic catalysts can also be obtained by adjusting metal ions for outstanding electrochemical reactions. In this study, various bimetallic zeolitic imidazolate framework (ZIF)-derived carbons were designed by varying the ratio of Zn to Co ions. Moreover, carbon nanotubes (CNTs) are added to improve the electrical conductivity further, ultimately leading to better electrochemical stability in the cathode. As a result, the optimized bimetallic ZIF–carbon/CNT composite exhibits a high discharge capacity of 16,000 mAh·g−1, with a stable cycling performance of up to 137 cycles. This feature is also beneficial for lowering the overpotential of the cathode during cycling, even at the high current density of 2,000 mA·g−1.

Constructing Bimetallic ZIF‐Derived Zn,Co‐Containing N‐Doped Porous Carbon Nanocube as the Lithiophilic Host to Stabilize Li Metal Anodes in Li−O2 Batteries

Li metal, because of its ultrahigh theoretical capacity, has attracted extensive attention. However, uncontrollable dendritic Li formation and infinite electrode dimensional variation hinder application of Li anodes. Herein, Zn,Co bimetallic zeolitic imidazolate frameworks (ZIFs) were synthesized and further pyrolyzed to obtain Zn,Co-containing N-doped porous carbon nanocube (Zn/Co-N@PCN), which was further applied as lithiophilic host to construct the lithiated Zn/Co-N@PCN (Li-Zn/Co-N@PCN). Zn vapor produced many pores on the carbon framework during calcination process that could store enough Li and thus inhibit the huge electrode volume change. Additionally, there were abundant lithiophilic groups in Zn/Co-N@PCN, such as N- or Co/Zn-based species, which were beneficial to uniform Li deposition. Moreover, the stable and conductive carbon-based matrix could ensure superior and reproducible Li plating/stripping behavior in Zn/Co-N@PCN over cycling. As a result, the Li-Zn/Co-N@PCN anode showed a steady and high columbic efficiency of around 99.0 % for 600 cycles at 0.5 mA cm-2 . The Li-Zn/Co-N@PCN-based Li-O2 battery could continuously work beyond 200 cycles, superior to a cell with a Li-Cu anode. These results in this work provide a novel way for construction of the advanced Li-based anodes and the corresponding high-performance Li-O2 batteries.

Introduction of a new active and stable cathode catalyst based on bimetal-organic frameworks/PPy-sheet for alkaline direct ethanol fuel cell

For the first time, the polypyrrole (PPy) with a sheet-like structure was synthesized by a high-efficiency and facile chemical reaction process. A new composite with the growth of bimetallic zeolitic imidazolate frameworks on polypyrrole sheet-like (BMZIF@PPy) was synthesized. Then, the BMZIF@PPy composite by different heat-treatment temperatures is applied to make oxygen reduction reaction (ORR) electrocatalysts. Electrochemical measurements perform to investigate the ORR properties in both acidic and alkaline media. The onset potential and the limiting current density for the Cobalt/Zinc-nanocarbon@polypyrrole pyrolysis at 800 °C (Co/Zn-NC@PPy-800) were 0.977 VRHE and 4.99 mA cm−2 in 0.1 M KOH and 0.85VRHE and 5.48 mA cm−2 in 0.5 M H2SO4. Finally, due to the good activity and stability in alkaline media, the Co/Zn-NC@PPy-800 electrocatalyst is used as the cathode in an alkaline direct ethanol fuel cell. The maximum power of the Co/Zn-NC@PPy-800 cathode catalyst was 77% higher than that of the commercial Pt/C electrocatalyst.

Growth control of Zeolitic Imidazolate Frameworks derived sulfides with the coexistence of nanosheets and nanoflowers for high performance supercapacitor

Metal organic frameworks can be used as precursors to design and construct nano materials with various structures Here, we use a bimetallic Zeolitic imidazolate frameworks structure as a precursor to adjust the morphology of the electrode material and enhance its performance. This bimetallic type ZIF structure increases the electrochemically active area, optimizes the electronic orbitals, changes the charge transfer paths, and modulates the electronic structure. Subsequently, ZnCo-ZIF precursor is vulcanized using thioacetamide as a sulfur source to obtain ZnCoS/0.2 M NH4F (ZCS/AF0.2) by a solvothermal method. Since the pH of the solution has a strong influence on the formation of the ZIF material during the preparation of the ZnCo-ZIF precursor, the pH of the solution is adjusted by NH4F to obtain the structure of nanosheets (2D) coexisting with nanoflowers (3D). ZCS/AF0.2 electrode achieves high specific capacitance of 3175.5 F g−1 at 1 A g−1, with good rate capability and cyclic stability. In addition, asymmetric supercapacitor devices using the ZCS/AF0.2 and active carbon as positive and negative electrodes are fabricated, delivering high energy density of 89.8 W h kg−1 at the power density of 1103.3 W kg−1 and 41.2 W h kg−1 at the power density of 21,500 W kg−1.

Rational Regulation of Co-N-C Coordination for High-Efficiency Generation of 1O2 toward Nearly 100% Selective Degradation of Organic Pollutants.

Single oxygen-based advanced oxidation processes (1O2-AOPs) exhibit great prospects in selective degradation of organic pollutants. However, efficient production of 1O2 via tailored design of catalysts to achieve selective oxidation of contaminants remains challenging. Herein, we develop a simple strategy to regulate the components and coordination of Co-N-C catalysts at the atomic level by adjusting the Zn/Co ratio of bimetallic zeolitic imidazolate frameworks (ZnxCo1-ZIFs). Zn4Co1-C demonstrates 98% selective removal of phenol in the mixed phenol/benzoic acid (phenol/BA) solutions. Density functional theory calculations and experiments reveal that more active CoN4 sites are generated in Zn4Co1-C, which are beneficial to peroxymonosulfate activation to generate 1O2. Furthermore, the correlation between the origin of selectivity and well-defined catalysts is systematically investigated by the electron paramagnetic resonance test and quenching experiments. This work may provide novel insights into selective removal of target pollutants in a complicated water matrix.

Synthesis of hollow Fe, Co, and N-doped carbon catalysts from conducting polymer-metal-organic-frameworks core-shell particles for their application in an oxygen reduction reaction

Oxygen reduction reaction (ORR), one of the key reactions for fuel cells and zinc-air batteries, should be improved for higher performance. Herein, we fabricated hollow Fe, Co, and nitrogen co-doped carbon (H-FeCo-NC) catalyst, which was prepared by carbonization of core-shell particles made of polypyrrole (PPy)-coated polystyrene (PS) spheres as cores and (Zn, Co) bimetallic-zeolitic imidazolate frameworks (ZnCoBZIFs) as shells. PPy was used as a nitrogen and a carbon source. The H-FeCo-NC catalyst had a high surface area of 324.08 m2 g−1 with uniformly distributed Fe and Co species, and excellent ORR performance with the half-wave potential of 0.888 V vs. reversible hydrogen electrode in alkaline media. Furthermore, the H-FeCo-NC catalyst demonstrated exceptional stability, durability, and tolerance to methanol crossover.

Ni single-atom sites supported on carbon aerogel for highly efficient electroreduction of carbon dioxide with industrial current densities

Finding highly efficient electrocatalysts for the CO2 electroreduction reactions (CO2RR) that have high selectivity and appreciable current density to meet commercial application standards remains a challenge. Because their reduction potentials are similar to that of the associated competitive hydrogen evolution reaction and the CO2 activation kinetics are sluggish. Although single-atom catalysts (SACs) with high atom efficiency are one class of promising candidates for the CO2RR to produce CO, single-atom active sites supported on microporous carbons are not fully exposed to substrates and thus lead to low current density. Carbon aerogels with interconnected channels and macropores can facilitate mass transport. But few reports describe utilizing them as supports to anchor SACs for efficient electrocatalysis. Herein, N-doped carbon aerogels supporting Ni single atomic catalyst sites (denoted as Ni-NCA-X, X ​= ​10, 20) were fabricated by pyrolyzing Ni/Zn bimetallic zeolitic imidazolate framework (Ni/Zn-ZIF-8)/carboxymethylcellulose composite gels. Owing to abundant hierarchical micro-, meso-, and macropores and high CO2 adsorption, the Ni single active sites in the optimal Ni-NCA-10 were readily accessible for the electrolyte and CO2 molecules and thus achieved an industrial-level CO partial current density of 226 ​mA ​cm−2, a high CO Faradaic efficiency of 95.6% at −1.0 ​V vs. the reversible hydrogen electrode, and a large turnover frequency of 271810 h−1 in a flow-cell reactor at −1.0 ​V. Such excellent CO2RR performance makes Ni-NCA-10 a rare state-of-the-art electrocatalyst for CO2-to-CO conversion. This work provides an effective strategy for designing highly efficient electrocatalysts toward the CO2RR to achieve industrial current density via anchoring single-atom sites on carbon aerogels.

Bimetallic ZIFs based on Ce/Zn and Ce/Co combinations for stable and enhanced carbon capture

Global warming leading to adverse climate changes has become a serious concern worldwide. Carbon capture through various technologies like adsorption has been found to be the most potential tool to address this phenomenon. In this work, novel, cost effective and green adsorbents like Zeolitic Imidazolate Frameworks (ZIFs) have been developed through simple protocols to give higher capture capacity and cyclic stability. Addressing global warming and mitigating climate change would provide the most conducive environment and ecosystem to promote efficiency, sustainability, and cleaner production in various processes. Also, carbon dioxide captured may be converted to clean fuels like Hydrogen through methanation. In this study, two bimetallic ZIFs, ((Ce,Zn)ZIF-8 and (Ce,Co)ZIF-67), were synthesized and chosen to compare with each other in terms of CC (Carbon Capture) performance. Response Surface Methodology (RSM), specifically Central Composite Design (CCD), was employed to aid in designing the carbon capture (CC) experiments. Four process parameters that influenced the CC performance were temperature, amount of adsorbent loaded, time of carbonation and effect of diethanolamine (DEA) loading. Both adsorbents showed good initial CC values with (Ce,Zn)ZIF-8 showing the better uptake value of 3.77 mmol/g than the uptake value of 3.55 mmol/g of (Ce,Co)ZIF-67. The highest absolute CC value of 4.55 mmol/g was given by 15% DEA loaded (Ce,Zn)ZIF-8 adsorbent. Temperature and DEA loading were the two most influential factors in CC uptake values, while the time of carbonation and amount of adsorbent had minimal effect individually. The pseudo-second-order and Avrami models best explained the CO2 uptake of (Ce,Zn)ZIF-8 and (Ce,Co)ZIF-67, respectively. Langmuir adsorption isotherm suited the experimental data well indicating a monolayer adsorption process. Both the adsorbents performed decently well when subjected to the cyclic adsorption process retaining up to 94% of their initial CO2 uptake over 15 cycles.

Bimetal Metal‐Organic Frameworks Derived Hierarchical Porous Cobalt@Nitrogen‐Doped Carbon Tubes as An Efficient Electrocatalyst for Oxygen Reduction Reaction

AbstractThe design and preparation of inexpensive, stable, and superior catalysts for the oxygen reduction reaction (ORR) are significant but challenging towards sustainable energy conversion technologies. Herein, a tubular template‐assisted strategy for fabrication of cobalt nanoparticles (Co NPs) embedded in one‐dimensional (1D) N‐doped porous tubular carbon composites (Co@N−CTs) is developed via in‐situ growth of bimetallic zeolitic imidazolate frameworks (ZnCo−ZIFs) on hollow polypyrrole (PPy) nanotubes surface. The PPy can not only act as a hollow tubular template, but also efficiently inhibit aggregation of Co NPs. Thanks to the 1D tubular interconnected networks and abundant micro‐/nano‐ porous tube wall structure, the as‐prepared Co@N−CTs catalyst achieves outstanding ORR performance with an onset potential (E0) of 0.982 V and a half‐wave potential (E1/2) of 0.864 V. Meanwhile, the Co@N−CTs catalyst also demonstrates superior durability with slightly decay of 3 % of initial current over 40000 s, as well as tolerance to the methanol. Furthermore, the Co@N−CTs cathode exhibits a large specific capacity (784 mAh g−1) and satisfying power density (116 mW cm−2) in a Zn‐air battery.