Open-framework Structure Research Articles

Zinc hexacyanoferrate with open framework for efficient aqueous cobalt ions storage

In this work, we report a high-performance aqueous Co-ion battery with zinc hexacyanoferrate as Co2+ storage material. Owing to the open framework, zinc hexacyanoferrate exhibits excellent electrochemical performance. The reversible capacity of zinc hexacyanoferrate is up to 62.4 mAh g−1 at 5C with ultralow capacity decay (0.0084 % per cycle) within 500 cycles. Even cycled at a higher rate of 10C, zinc hexacyanoferrate still can remain a high capacity retention of 98.8 % after 700 cycles. The excellent electrochemical performance is attributed to the rapid kinetics behavior of Co2+ in the open and stable framework structure. Besides, a joint analysis of in-situ X-ray diffraction, ex-situ Fourier transform infrared spectroscopy and ex-situ X-ray photoelectron spectroscopy verifies the highly reversible structural change of zinc hexacyanoferrate during charge/discharge process. All these evidences suggest that zinc hexacyanoferrate may be a promising host material for Co2+ storage in aqueous rechargeable batteries.

Zero-Strain Sodium Nickel Ferrocyanide as Cathode Material for Sodium-Ion Batteries with Ultra-Long Lifespan.

Prussian blue analogues are recognized as one of the most promising cathode materials for sodium-ion batteries (SIBs) owing to the open 3D framework structure with large interstitial sites and developed Na-ion diffusion channels. However, high content of anion vacancy and poor structural stability have hampered the prospect of their application. In this work, sodium nickel ferrocyanide (Na1.34Ni[Fe(CN)6]0.92, NNHCF) is proposed as cathode material for SIBs. N-coordinated Ni-ion can boost NNHCF to possess less Fe[(CN)6]4- defect, low Na-ion migration barrier, and more negative formation energy compared with Na0.91Cu[Fe(CN)6]0.77 (NCHCF), thus exhibiting more active sites, fast electrochemical kinetics behavior and great structure stability. It is confirmed that NNHCF undergoes a solid solution mechanism without phase evolution for reversible Na-ion intercalation/deintercalation, employing Fe associated with C atom as redox center for charge compensation. Therefore, NNHCF contributes a high initial energy density of 180.94 Wh·g-1 at 10 mA·g-1, excellent rate capability, superior cycling stability with ultra-long lifespan of 13000 cycles, and low fading rate of 0.0027% per cycle at 500 mA·g-1. This work sheds light on the construction of low-defect PBA cathodes with outstanding dynamics and stability.

Synthesis, Structure, and Actual Applications of Double Metal Cyanide Catalysts.

Double metal cyanide (DMC) complexes represent a unique family of materials with an open framework structure. The main current application of these complexes in chemical industry is their use as catalysts (DMCCs) of the ring-opening polymerization of propylene oxide (PO), yielding branched polyols, highly demanded in production of polyurethanes and surfactants. The actual problem of chemical fixing carbon dioxide from the atmosphere gave new impetus to the development of DMCCs, which turned out to be effective in oxirane/CO2 copolymerization. In recent years, new types and formulations of DMCCs were created, so that greater understanding of the reaction mechanisms was achieved and new fields of catalytic applications were found. In the present review, we summarized background and actual information about the synthesis, structure, and mechanisms of the action of DMCCs, as well as their application in the development of new materials and fine chemicals.

A self-powered photoelectrochemical aptasensor using 3D-carbon nitride and carbon-based metal-organic frameworks for high-sensitivity detection of tetracycline in milk and water.

Antibiotic residues have become a significant challenge in food safety, threatening both ecosystem integrity and human health. To combat this problem, we developed an innovative photo-powered, self-powered aptasensor that employs a novel carbon-doped three-dimensional graphitic carbon nitride (3D-CN) combined with a metal-organic framework composed of N-doped copper(I) oxide-carbon (Cu2O@C) skeletons. The 3D-CN serves as the photoanode, offering stable photocurrent production due to its three-dimensional open framework structure. The N-doped Cu2O@C acts as the photocathode, providing oxidation protection for the metal core and enhancing light absorption due to its metal-organic framework structure. A key feature of our work is exploiting the Fermi level difference between the n-type photoanode and p-type photocathode, which facilitates faster migration of photogenerated electrons toward the photocathode, thereby enhancing the sensor's self-powered effect. Experimental results reveal that upon aptamer loading, the sensor can linearly detect tetracycline (TC) within a range of 0.5pmol/L to 300nmol/L, with a detection limit as low as 0.13pmol/L. It also demonstrates excellent selectivity, stability, and reproducibility, making it applicable to real samples such as milk and river water. Consequently, our research provides a highly efficient and sensitive method for monitoring TC in food, with significant practical implications and profound impacts on food safety.

First copper (II) oxo-selenite-sulfate Cu4O(SeO3)(SO4)2 and the role of a lone electron pair in open framework crystal structure formation

New copper oxo-selenite-sulfate Cu4O(SeO3)(SO4)2 was prepared by the reaction of anhydrous CuSO4, CuO, and SeO2 in a sealed silica tube. The compound crystallizes in the triclinic P1‾ space group, with cell parameters a = 8.379(3)Å, b = 8.402(4) Å, c = 8.497(3) Å, α = 82.988(14) °, β = 61.006(9) °, γ = 62.105(14)°. The selenite-sulfate features open-framework crystal structure with two types of channels, where lone electron pairs of SeO32− groups are located. DFT calculations were made to support this statement and to investigate the nature of chemical bonding in the crystal structure and estimate the band gap (3.3 eV).The crystal structure of Cu4O(SeO3)(SO4)2 was compared to the related triclinic form of Cu4O(SeO3)3. The role of sulfate groups is also discussed.

Simultaneous Tailoring of Chemical Composition and Morphology Configuration in Metal Hexacyanoferrate for Ultrafast and Durable Sodium‐ion Storage

Metal hexacyanoferrates (MHCFs) with adjustable composition and open framework structures have been considered as intriguing cathode materials for sodium‐ion batteries (SIBs). Exploiting MHCFs with ultrafast and durable sodium storage capability as well as comparable capacity is always a goal that many investigators pursue, but remains challenging. Herein, simultaneous tailoring of chemical composition and morphology configuration is carried out to design a hollow monoclinic high‐entropy MHCF (HMHE‐HCF) assembled by nanocubes for the first time to realize the objective. The “cocktail effect” of high‐entropy construction, rich sodium content of monoclinic phase, and unique hollow structure endow HMHE‐HCF cathode with fast reaction kinetics and energetically stable performance during continuous charging/discharging processes. As a result, the HMHE‐HCF cathode demonstrates superior rate performance up to an ultra‐high rate of 100 C (71.1% retention to 0.1 C), and remarkable cycling stability with a capacity retention of 77.8% over 25,000 cycles at 100 C, outperforming most reported sodium‐ion cathodes. Further, the HMHE‐HCF//hard carbon full‐cell delivers capacities of 99.0 and 82.3 mAh g–1 at 0.1 C and 10 C, respectively, and retains 98.1% of the initial capacity after 1,600 cycles at 5C, demonstrating its potential application for sodium‐ion storage.

Simultaneous Tailoring of Chemical Composition and Morphology Configuration in Metal Hexacyanoferrate for Ultrafast and Durable Sodium-ion Storage.

Metal hexacyanoferrates (MHCFs) with adjustable composition and open framework structures have been considered as intriguing cathode materials for sodium-ion batteries (SIBs). Exploiting MHCFs with ultrafast and durable sodium storage capability as well as comparable capacity is always a goal that many investigators pursue, but remains challenging. Herein, simultaneous tailoring of chemical composition and morphology configuration is carried out to design a hollow monoclinic high-entropy MHCF (HMHE-HCF) assembled by nanocubes for the first time to realize the objective. The "cocktail effect" of high-entropy construction, rich sodium content of monoclinic phase, and unique hollow structure endow HMHE-HCF cathode with fast reaction kinetics and energetically stable performance during continuous charging/discharging processes. As a result, the HMHE-HCF cathode demonstrates superior rate performance up to an ultra-high rate of 100 C (71.1% retention to 0.1 C), and remarkable cycling stability with a capacity retention of 77.8% over 25,000 cycles at 100 C, outperforming most reported sodium-ion cathodes. Further, the HMHE-HCF//hard carbon full-cell delivers capacities of 99.0 and 82.3 mAh g-1 at 0.1 C and 10 C, respectively, and retains 98.1% of the initial capacity after 1,600 cycles at 5C, demonstrating its potential application for sodium-ion storage.

Unlocking the potential: strategic synthesis of a previously predicted pyrazolate-based stable MOF with unique clusters and high catalytic activity.

The metal-organic framework (MOF) constructed from [Co4Pz8] clusters (Pz = pyrazolate) and 1,3,5-tris(pyrazolate-4-yl) benzene (BTP3-) ligands was structurally predicted many years ago, and expected to be a promising candidate for various applications owing to its unique clusters and highly open 3D framework structure. However, this MOF has not been experimentally prepared yet, despite extensive efforts were made. In this work, we present the successful construction of this MOF, hereinafter referred to as BUT-124(Co), by adopting a two-step synthesis strategy, involving the initial construction of a template framework (BUT-124(Cd)) followed by a post-synthetic metal metathesis process. The effects of various cobalt sources and solvents were systematically investigated, and an innovative stepwise metathesis strategy was employed to optimize the exchange rates and the porosity of the material. BUT-124(Co) demonstrates high catalytic activity in the oxygen evolution reaction (OER), achieving a competitive performance with an overpotential of 393 mV at a current density of 10 mA cm-2, and also affords remarkable long-term stability during potentiostatic electrolysis in 1 M KOH solution, surpassing the durability of many benchmark catalysts. This work not only introduces a novel MOF material with promising properties but also exemplifies a strategic synthesis approach for pyrazolate-based MOFs, paving the way for advancements in diverse application fields.

(Invited) Selective Ammonia Separation Using Prussian Blue Analogues

Prussian blue analogues (PBAs) are a three-dimensional coordination polymer with iron and transition metals bridged with cyanide ligands, creating open-framework structures for hosting guest ions into interstitial sites. These sites can be occupied by cations via adsorption/desorption or intercalation/deintercalation, which has been widely utilized in developing separation processes and energy storage devices. Additionally, it has been well established that the size of the channel provides selectivity between monovalent cations based on their hydrated radii. Using these unique functionalities allows for selective ammonia recovery from wastewater. The feasibility of selective separation has been demonstrated using PBA-based electrodes that showed reversible and selective intercalation/deintercalation of NH4 + by cyclic operation. To enable continuous separation, we recently developed an electrochemically driven membrane process, where PBAs provided selective ion-conducting channels. An improved selectivity for NH4 + relative to Na+ was achieved using synthetic and domestic wastewaters, which was attributed to a thin layer of PBA created on the surface of a cation exchange membrane. These results collectively show that the use of PBAs for selective ammonia separation could lead to the development of efficient electrochemical processes for nutrient recovery.

Multi-metal substituted Fe-based Prussian blue as high-capacity cathode material for potassium ion batteries

Fe-based Prussian blue (FePB) has been widely studied as cathode materials of potassium ion batteries due to its three-dimensional open framework structure and large ion migration channels. In this study, the effect of the introduction of various metals (Co2+, Cu2+, Ni2+, Mn2+) on the rate and cycle properties of FePB was investigated. MnCoNiFePB cathode material shows better electrochemical performance, with the initial discharge capacity of 91.3 and 75.4 mAh g−1 (capacity retention is 56.7 % after 100 cycles) at 0.2C and 1C, respectively. These results inspire new ideas for the development and application of potassium ion battery electrode materials.

High-Entropy Prussian Blue Analogues as High-Capacity Cathode Material for Potassium Ion Batteries

Potassium ion batteries, due to their similar electrochemical principles to lithium-ion batteries and the abundance of metal sources, are considered one of the alternatives to lithium-ion batteries. The development of new cathode materials has always been a research focus in this field. Among them, Prussian blue materials, with their three-dimensional open and flexible metal framework structure, can efficiently and reversibly store potassium ions. However, Prussian blue cathode materials still face issues such as poor reversibility and low capacity, which limit their application scope. This study investigates the preparation of high-entropy Prussian blue analogues materials to enhance electrochemical performance. The doping of five different transition metals (Fe2⁺, Co2⁺, Cu2+, Ni2+, and Mn2+) sharing the same nitrogen coordination sites results in a configurational entropy greater than 1.5 R for the material. HEPB-1 cathode material (K1.75Mn0.26Fe0.01Ni0.01Cu0.08Co0.09 [Fe(CN)6]0.66·0.83H2O) shows better electrochemical performance, with the initial discharge capacity of 86.69 and 74.51 mAh g−1 (capacity retention is 75.2% after 100 cycles) at 20 and 100 mA g−1, respectively. The research results have provided new insights for the further development and application of potassium ion batteries.

Polyaniline-modified amorphous tin-based Prussian blue analogue as cathodes for long-life aqueous zinc ion batteries

Prussian blue analogs (PBAs) have emerged in the field of aqueous zinc ion batteries (AZIBs) owing to their simple synthesis method and three-dimensional open framework structure. Although PBAs have high redox potentials, the unsatisfactory specific capacity and poor electrical conductivity limit their development to some extent. In this work, amorphous tin hexacyanoferrate (SnHCF) and polyaniline (PANI) were combined to form SnHCF/PANI composite. The synergistic effect of the amorphous structure of SnHCF and PANI with good conductivity makes the SnHCF/PANI electrode exhibit excellent redox activity and achieve rapid ion/electron transfer. When used as a cathode in AZIBs, the SnHCF/PANI provides a high specific capacity (136.8 mAh g−1 at 0.5 A g−1) and excellent cycling stability (a discharge specific capacity of 54.3 mAh g−1 after 2500 cycles at 2 A g−1). This work offers a new idea for the development of PBAs-based composites as cathode materials for AZIBs.

Design of Multivariate Biological Metal-Organic Frameworks: Toward Mimicking Active Sites of Enzymes.

Mimicking enzymatic processes carried out by natural enzymes, which are highly efficient biocatalysts with key roles in living organisms, attracts much interest but constitutes a synthetic challenge. Biological metal-organic frameworks (bioMOFs) are potential candidates to be enzyme catalysis mimics, as they offer the possibility to combine biometals and biomolecules into open-framework porous structures capable of simulating the catalytic pockets of enzymes. In this work, we first study the catalase activity of a previously reported bioMOF, derived from the amino acid L-serine, with formula {CaIICuII6[(S,S)-serimox]3(OH)2(H2O)} · 39H2O (1) (serimox = bis[(S)-serine]oxalyl diamide), which is indeed capable to mimic catalase enzymes, in charge of preventing cell oxidative damage by decomposing, efficiently, hydrogen peroxide to water and oxygen (2H2O2 → 2 H2O + O2). With these results in hand, we then prepared a new multivariate bioMOF (MTV-bioMOF) that combines two different types of bioligands derived from L-serine and L-histidine amino acids with formula CaIICuII6[(S,S)-serimox]2[(S,S)-hismox]1(OH)2(H2O)}·27H2O (2) (hismox = bis[(S)-histidine]oxalyl diamide ligand). MTV-bioMOF 2 outperforms 1 degrading hydrogen peroxide, confirming the importance of the amino acid residue from the histidine amino acid acting as a nucleophile in the catalase degradation mechanism. Despite displaying a more modest catalytic behavior than other reported MOF composites, in which the catalase enzyme is immobilized inside the MOF, this work represents the first example of a MOF in which an attempt is made to replicate the active center of the catalase enzyme with its constituent elements and is capable of moderate catalytic activity.

Can Prussian Blue Analogues be Holy Grail for Advancing Post‐Lithium Batteries?

The recent classification of lithium as a critical raw material surged the R&D of post‐lithium batteries (PLBs). The larger cation charge carriers of these PLBs consequently entailed extensive materials R&D for battery components, especially cathode. Prussian Blue (PB) and its analogues (PBAs) have emerged as promising cathode materials for PLBs due to their desirable characteristics, including a three‐dimensional open framework structure that facilitates fast ion diffusion for both monovalent (Li+, Na+, K+) and multivalent (Mg2+, Ca2+, Zn2+, Al3+) ions, stable framework structures, electrochemical tunability, availability of widely used precursors, and ease of synthesis. Our comprehensive review reveals that several challenges are yet to be addressed in employing PBAs as cathode materials for PLBs, viz., vacancies, crystal water, side reactions, and conductivity issues due to electrochemically inactive components of PBAs. This review paper provides an exhaustive survey of material development, including the mitigation strategies of the challenges in employing PBAs as cathode materials for advancing PLBs.

Tungsten Doping of Two‐Dimensional VO2 Nanoribbons for Rapid Zinc Ion Storage Channels

AbstractVanadium‐based oxides are promising candidates for use in aqueous zinc‐ion batteries owing to their open framework structure that facilitates rapid Zn2+ deintercalation. To improve the kinetics, a two‐dimensional nanoribbon‐shaped W‐VO2 cathode material was developed by pre‐embedding tungsten atoms into VO2(B) using a one‐step hydrothermal method. The large interlayer spacing in the W‐VO2 nanosheets aided in the deintercalation of hydrated Zn2+ ions. The 1 % W‐doped electrode exhibited stable cycling, reaching a high capacity of 365.8 mAh g−1 at 0.3 A g−1, with a 92.6 % capacity retention (338.8 mAh g−1) after 200 cycles. Impressively, 84.3 % of the capacity is retained after 1200 cycles at 1 A g−1. The zinc storage mechanism of W‐VO2 was elucidated through in situ X‐ray diffraction and X‐ray photoelectron spectroscopy, highlighting the benefits of tungsten doping on tunnel structure stability and Zn2+ deintercalation reversibility in VO2 electrodes.

Exploiting the Reactivity of Metal Trifluoroacetates to Access Alkali-Niobium(V) Oxyfluorides.

Motivated by the lack of facile routes to alkali-niobium(V) oxyfluorides KNb2O5F and CsNb2O5F, we investigated the reactivity of alkali trifluoroacetates KH(tfa)2 and CsH(tfa)2 (tfa = CF3COO-) toward Nb2O5 in the solid state. Tetragonal tungsten bronze KNb2O5F and pyrochlore CsNb2O5F were obtained by simply reacting the corresponding trifluoroacetate with Nb2O5 at 600 °C under air, without the need for specialized containers or a controlled atmosphere. Thermolysis of KH(tfa)2 in the presence of Nb2O5 yielded single-phase polycrystalline KNb2O5F. By contrast, the reaction between CsH(tfa)2 and Nb2O5 produced a mixture of CsNb2O5F and a new oxyfluoride of formula CsNb3O7F2, whose crystal structure was solved using powder X-ray and electron diffraction. CsNb3O7F2 (space group P6/mmm) belongs to the family of hexagonal tungsten bronzes and features an open-framework structure consisting of corner-sharing Nb(O,F)6 octahedra with hexagonal channels occupied by Cs+ ions. Isomorphous RbNb3O7F2 was obtained upon reacting RbH(tfa)2 with Nb2O5. Synthetic optimization enabled the preparation of RbNb3O7F2 and CsNb3O7F2 as single-phase polycrystalline solids at 500 °C under flowing synthetic air. Both oxyfluorides were found to be semiconductors with a band gap of ≈3.5 eV. The discovery of these two oxyfluorides highlights the importance of probing the reactivity of solids whose full potential as fluorinated precursors is yet to be realized.

Cations-Pillared and Polyaniline-Encapsulated Vanadate Cathode for High-Performance Aqueous Zinc-Ion Batteries.

Layered vanadium-based oxides have emerged as highly promising candidates for aqueous zinc-ion batteries (AZIBs) due to their open-framework layer structure and high theoretical capacity among the diverse cathode materials investigated. However, the susceptibility to structural collapse during charge-discharge cycling severely hampers their advancement. Herein, we propose an effective strategy to enhance the cycling stability of vanadium oxides. Initially, the structural integrity of the host material is significantly reinforced by incorporating bi-cations Na+ and NH4 + as "pillars" between the V2O5 layers (NaNVO). Subsequently, surface coating with polyaniline (PA) is employed to further improve the conductivity of the active material. As anticipated, the assembled Zn//NaNVO@PA cell exhibits a remarkable discharge capacity of 492 mAh g-1 at 0.1 A g-1 and exceptional capacity retention up to 89.2 % after 1000 cycles at a current density of 5 A g-1. Moreover, a series of in-situ and ex-situ characterization techniques were utilized to investigate both Zn ions insertion/extraction storage mechanism and the contribution of polyaniline protonation process towards enhancing capacity.

Na3[Al2B6P4O22(OH)3](H2O)6 and Na3[Al2BP2O11](H2O)0.5: Two Remarkable Complex Aluminum Borophosphates.

Two remarkable aluminum borophosphates (AlBPOs), namely, Na3[Al2B6P4O22(OH)3](H2O)6 (denoted as ABPO1) and Na3[Al2BP2O11](H2O)0.5 (denoted as ABPO2), have been designed and prepared by low-temperature flux syntheses. The exceptional open framework structure of ABPO1 is formed by a unique microanionic network [Al2B6P4O22(OH)3]n3-, which contains three types of 8-, 12-, and 16-membered ring (MR) tunnels. Interestingly, these tunnels are featured by a type of super-nanocage as large as ∼1.753 nm × 1.753 nm × 1.753 nm, which is the first example of AlBPOs containing extra-large cages. Importantly, it was found that Na+ can be partially exchanged by K+, Sr2+, Cd2+, and Ni2+, which means that it is a potential ionic exchanger for removing radionuclides and toxic cations. The structure of ABPO2 features a unique 2D anionic AlBPO layer composed of corner-sharing AlO6 octahedra and AlO4, BO4, and PO4 tetrahedra. To the best of our knowledge, this is the first example of both AlO6 octahedra and AlO4 tetrahedra being contained in the structure. 9-MRs can be observed along the b-axis. Herein, the syntheses and topological structures of ABPO1 and ABPO2 as well as elemental analysis, thermal stability, infrared spectroscopy, UV-vis diffuse reflectance, structural properties, and ionic exchange properties are also discussed.

Orthorhombic K3V3(PO4)4: A low-temperature cathode material for potassium-ion batteries

Potassium-ion battery has been considered as a promising energy storage device with low cost and high sustainability. However, its low-temperature performance is always poor due to the large size of K+ ions and poor ion transportation capability under low temperature. In this work, a carbon-coated orthorhombic K3V3(PO4)4/C cathode material for potassium-ion batteries is developed with promising low-temperature cycle performance. At −10 °C, K3V3(PO4)4/C retains a reversible capacity of 52.2 mAh/g for 1400 cycles at a current density of 100 mA g−1. The superior low-temperature performance is attributed to its open framework structure, which provides three-dimension channels for K-ion transportation. It is revealed that V3+/V4+ redox dominates the charge compensation in K3V3(PO4)4/C during charge and discharge processes. Carbon coating can not only reduce the charge transfer resistance of the electrode and prevent electrode cracking, but also helps to the formation of CF3-rich interfaces between the cathode and electrolyte, ensuring high interfacial stability of K3V3(PO4)4/C during cycling.

Prussian Blue Nanoplates for Potassium Ion Battery Cathode with High Capacity and High Energy Density

AbstractPrussian blue analogues (PBAs) represent as a class of materials with an open framework structure and have been intensively explored as the potential active materials for alkaline‐ion batteries. Here, we present the synthesis of Prussian blue nanoplates designed for use as high performance cathode materials in potassium‐ion batteries. Prussian blue nanoplates were synthesized through a facile solution precipitation route using a highly concentrated potassium citrate solution. The potassium‐rich environment during the synthesis facilitated horizontal growth of the crystals, yielding potassium‐rich Prussian blue nanoplates. The resultant Prussian blue nanoplates exhibited a significantly larger particle size of 600 nm and a reduced specific surface area of 6.8 m2 g−1, compared to conventionally synthesized Prussian blue hexahedrons. Half‐cell tests demonstrated that the Prussian blue nanoplates exhibited a high gravimetric capacity of 152.5 mAh g−1 with a nominal voltage 3.952 V at a C‐rate of 0.1 C, yielding an energy density of 602.7 Wh kg−1. Cycling tests demonstrated high cycling stability of the material, maintaining a capacity of 122.7 mAh g−1 and a nominal voltage of 3.923 V after 200 cycles at 0.2 C. In a full‐cell configuration with graphite anodes, a gravimetric capacity changed from 134.1 mAh g−1 to 108.9 mAh g−1 after 100 cycles at 0.2 C, demonstrating a good cycling stability. This work provides a new insight into the electrochemical properties of Prussian blue nanoplates and highlights their potential as high‐performance cathode materials for potassium‐ion batteries.