Metal-organic Framework Templates Research Articles

ZIF-67 derivatives of NiCo2S4 Decorated in Salen-Complex Amine Functionalization GO Layers for High-Performance Applications in Supercapacitor Devices.

The study develops polyamine-functionalized graphene oxide-supported NiCo2S4 nanomaterial using a metal-organic framework (MOF). This modification adds free amines and oxygen functionality to the graphene oxide electrode surface, resulting in the decrease in the 2 theta value from 11.2 to 7.1 and an increase in the interlayer spacing value from 1.4 to 7.8 nm. This modification enhances the surface properties, leading to improved wettability and dispersion stability. Additionally, bimetallic nanoparticles of NiCo2S4, synthesized via the ZIF-67 MOF template, further enhance performance. Analysis confirms the successful fabrication of ZIF-67/f-GO/NiCo2S4 electrode material through various techniques such as XPS spectra, FE-SEM, XRD, and Raman spectra. The resulting Salen-fGO@NiCo2S4 composite exhibits impressive specific capacitance, reaching 2581.65 F g-1 at 10 A g-1 with 82% capacity retention after 5000 cycles. Employing this composite in a hybrid supercapacitor yields remarkable energy and power densities of 40 and 920 W kg-1, individually, while maintaining 74% capacity retention rate at 10 A g-1. These findings offer promising prospects for advanced energy storage applications.

MOF-on-MOF Growth: Inducing Naturally Nonpreferred MOFs and Atypical MOF Growth.

ConspectusOverflowing metal-organic frameworks (MOFs) have been synthesized from a wide range of metal and organic components for specific purposes and intellectual curiosity. Each MOF has unique chemical and structural characteristics directed by the incorporated components, metal ions (or clusters), organic linkers, and their intrinsic coordination interactions. These incorporated components and structural characteristics are two pivotal factors influencing MOFs' fundamental properties and subsequent applications. Therefore, selecting the appropriate metal and organic components, considering their innate chemical and structural properties, is crucial to endow the final MOFs with the desired properties. Ultimately, producing MOFs with a desired structure using ideal components is the best approach to achieving the best MOFs tailored for specific purposes with desired properties. However, achieving MOFs with the intended structure from chosen components remains underdeveloped. In many cases, the resulting MOF structure is governed by the thermodynamically and/or kinetically preferred configuration (refers to a naturally preferred structure) of the chosen components and given reaction conditions. Additionally, producing hybrid MOFs with complex components, structures, and morphologies presents a great opportunity to obtain special MOFs with advanced properties and functions. In this Account, we outline our group's efforts over the past few years to develop naturally nonpreferred MOFs through the induced MOF-on-MOF growth process and atypical hybrid MOFs via nonstandard MOF-on-MOF growth. First, we highlight the prime strategy for producing naturally nonpreferred MOFs based on template-induced MOF-on-MOF growth. In this section, we discuss the two basic growth behaviors, isotropic and anisotropic growth of naturally nonpreferred MOFs, determined by the degree of matching between the cell lattices of the two MOFs. Second, we introduce the MOF farming concept for the productive cultivation and effective harvesting of naturally nonpreferred MOFs made by MOF-on-MOF growth. Here we discuss the importance of selecting the ideal MOF template for productive growth and developing an efficient method for harvesting cultivated MOFs. Next, we describe atypical anisotropic MOF-on-MOF growths between two MOFs with mismatched cell lattices. In this section, we introduce tip-to-middle MOF-on-MOF growth involving self-structural adjustment of the secondary MOF, logical inference of unidentified MOF structures based on MOF-on-MOF growth behavior and morphological features, and MOF-on-MOF growth accompanied by etching and transformation of the template. Finally, we discuss the perspectives and challenges of MOF-on-MOF growth and the synthesis of naturally nonpreferred MOFs. We hope that this Account offers valuable insights into the rational design and development of MOFs with desired structural and compositional characteristics, leading to the creation of ideal MOFs.

Capillary-driven microchip integrated with nickel phosphide hybrid-modified electrode for the electrochemical detection of glucose

BackgroundTransition metal phosphides with properties similar to platinum metal have received increasing attention for the non-enzymatic detection of glucose. However, the requirement of highly corrosive reagent during sample pretreatment would impose a potential risk to the human body, limiting their practical applications. ResultsIn this study, we report a self-powered microfluidic device for the non-enzymatic detection of glucose using nickel phosphide (Ni2P) hybrid as the catalyst. The Ni2P hybrid is synthesized by pyrolysis of metal-organic framework (MOF)-based precursor and in-situ phosphating process, showing two linear detection ranges (1 μM–1 mM, 1 mM–6 mM) toward glucose with the detection limit of 0.32 μM. The good performance of Ni2P hybrid for glucose is attributed to the synergistic effect of Ni2P active sites and N-doped porous carbon matrix. The microchip is integrated with a NaOH-loaded paper pad and a capillary-based micropump, enabling the automatic NaOH redissolution and delivery of sample solution into the detection chamber. Under the optimized condition, the Ni2P hybrid-based microchip realized the detection of glucose in a user-friendly way. Besides, the feasibility of using this microchip for glucose detection in real serum samples has also been validated. SignificanceThis article presents a facile fabrication method utilizing a MOF template to synthesize a Ni2P hybrid catalyst. By leveraging the synergy between the Ni2P active sites and the N-doped carbon matrix, an exceptional electrochemical detection performance for glucose has been achieved. Additionally, a self-powered chip device has been developed for convenient glucose detection based on the pre-established high pH environment on the chip.

Investigating the Catalytic Impact of Iron-Based Metal–Organic Framework Templates on the CO 2 -Derived Fischer–Tropsch Synthesis Process

Investigating the Catalytic Impact of Iron-Based Metal–Organic Framework Templates on the CO ₂ -Derived Fischer–Tropsch Synthesis Process

Hierarchical synthesis of binary ZnO@MWCNTs heterogeneous photocatalyst derived from porous Zn metal organic framework (MOF) template: Study on the effective photodegradation of Congo red (CR) dye

This study presents the synthesis of a heterogeneous ZnO@MWCNTs photocatalyst through a solvothermal method, employing a Zn-metal organic framework (MOF) template. The resulting nanocomposite showcases ZnO nanorods integrated with MWCNTs, forming a material characterized by nanosized building blocks, a substantial specific surface area, robust pore structure, and uniform morphology. A comprehensive XRD characterization reveals crystalline ZnO nanorods proficiently loaded onto the MWCNTs surface, forming a cohesive nano-composite. The inclusion of MWCNTs influences crystal growth, reducing crystallite size and altering optical absorption due to surface Plasmon resonance. This leads to a higher concentration of surface hydroxyl groups in the ZnO framework. Additionally, MWCNTs act as electron sinks, significantly reducing ZnO photooxidation and enhancing overall photostability in the composite. The photocatalytic efficacy of the composite in Congo Red (CR) degradation is impressive, achieving 92% degradation within 90 min of UV light exposure. A proposed photocatalytic mechanism elucidates the heightened performance of the synthesized photocatalysts. Notably, the MOF-derived ZnO@MWCNTs exhibited superior dye adsorption capacity compared to alternative adsorbents. This work underscores the immense potential of the ZnO@MWCNTs nanocomposite as a highly efficient photocatalyst for environmental remediation, offering significant advancements in dye degradation and wastewater treatment technologies.

Engineering lattice oxygen mobility and optimizing reaction pathway via tuning Cu-Co interactions for efficient elimination of volatile organic compounds: A metal–organic framework template approach

Incorporating a secondary metal into individual cobalt oxides has been viewed as an efficacious approach in creating intermetallic interactions. Nonetheless, the processes involved in the construction of intermetallic interactions, as well as the underlying mechanisms that contribute to catalytic activity, remain largely elusive in current scientific understanding. In this work, a range of Cu-Co bimetallic oxides were synthesized through various preparation methods, employing MOFs as templates. Notably, the hydrothermally-synthesized Cu/Co-HT catalyst exhibited impressive catalytic qualities for toluene combustion, with T50 = 229 °C and T90 = 239 °C, alongside exceptional stability and moisture resistance (under 10 vol. % of water) for at least 100 h. The optimal catalyst Cu/Co-HT is attributed to the stronger Cu-Co interaction, which leading to larger specific surface area and weaker Co-O bond strength. And it also affects the chemical properties, such as get more Co3+ and lattice oxygen species by a redox (Co2++Cu2+→Co3++Cu+), better electron transfer performance and low-temperature reducibility. In addition, the reaction mechanism of toluene over the surface of Cu/Co-HT was also revealed by in-situ DRIFTS. It was observed that the bimetallic catalyst, characterized by robust Cu-Co interactions, optimized the reaction pathway for toluene oxidation compared to pure Co3O4. This facilitation led to the direct conversion of benzyl alcohol into benzoate and carboxylate, thereby bypassing the intermediate step involving benzaldehyde, which enhancing the reaction speed, yielding a long-term stable and efficient operational performance. This study reveals that optimize the physicochemical properties of catalytic by enhancing bimetallic interactions is an effective strategy for improving catalytic behavior.

(Invited) MOF-Derived Nanosheet Arrays As Advanced Electrocatalysts for Water Splitting

Developing efficient, nanostructured electrocatalysts with desired compositions and structures is of great significance for improving the efficiency of water splitting toward hydrogen production. In this regard, metal organic framework (MOF) derived nanoarrays have attracted great attention as promising electrocatalysts because of their diverse compositions and adjustable structures. This presentation summarizes our recent work on the design and fabrication of MOF-derived nanosheet arrays toward enhanced catalytic activity for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) as well as overall water splitting.First, heterostructured inter-doped ruthenium-cobalt oxide ((Ru-Co)Ox) hollow nanosheet arrays were prepared on carbon cloth for efficient overall water splitting. Benefiting from the desirable compositional and structural advantages of more exposed active sites, optimized electronic structure, and interfacial synergy effect, the (Ru-Co)Ox nanoarrays exhibited outstanding performance as a bifunctional catalyst. Particularly, they showed a remarkable hydrogen evolution reaction (HER) activity with an overpotential of 44.1 mV at 10 mA cm–2 and a small Tafel slope of 23.5 mV dec–1, as well as an excellent oxygen evolution reaction (OER) activity with an overpotential of 171.2 mV at 10 mA cm−2. As a result, a very low cell voltage of 1.488 V was needed at 10 mA cm–2 for alkaline overall water splitting.Second, Mo-doped ruthenium–cobalt oxide (Mo-RuCoOx) nanosheet arrays were produced for high-efficiency water splitting through combining electronic and vacancy engineering. The unique Mo-RuCoOx nanosheet arrays were able to act as a high-performance bifunctional electrocatalyst toward both HER and OER. Theoretical calculations and experimental results reveal that the incorporation of Ru and Mo can effectively tune the electronic structure, and the controllable Mo dissolution coupling with the oxygen vacancy generation during surface reconstruction is able to optimize the adsorption energy of hydrogen/oxygen intermediates, thus greatly accelerating the kinetics for both HER and OER. As a result, the Mo-RuCoOx nanoarrays exhibit remarkably low overpotentials of 41 mV and 156 mV at 10 mA cm–2 for HER and OER in 1 M KOH, respectively. Furthermore, the two-electrode electrolyzer assembled by the Mo-RuCoOx nanoarrays requires a cell voltage as low as 1.457 V to achieve 10 mA cm–2 for alkaline overall water splitting.Third, hollow nanosheet arrays assembled by ultrafine ruthenium-cobalt phosphide nanocrystals were fabricated toward exceptional pH-universal hydrogen evolution. The development of high-efficiency electrocatalysts for pH-universal HER is promising for constructing feasible water splitting systems at all pH values, but it remains challenging. A facile approach toward hollow nanosheet arrays assembled by ultrafine ruthenium-cobalt phosphide (Ru-CoxP) nanocrystals was developed through conversion from the MOF template. The synergic effects of optimized electronic structure, increased active sites, and rapid charge/mass transfer endowed the Ru-CoxP nanoarrays with outstanding electrocatalytic performance toward pH-universal HER. While exhibiting remarkably low overpotentials of 34.6 mV and 22.7 mV at 10 mA cm–2 in 1 M KOH and 0.5 M H2SO4, respectively, the Ru-CoxP nanoarrays showed an extremely low overpotential of 21.6 mV at 10 mA cm–2 in 1 M phosphate buffer solution (PBS). Furthermore, they were able to stably drive a Pt-free neutral electrolyzer for overall water splitting at 10 mA cm−2 with a cell voltage as low as 1.557 V.

Improved rate capability and long cycle life of metal-organic framework derived TiO2@V2O5 composite as an efficient cathode for sodium-ion batteries

Vanadium oxide on carbon nanoporous structure (V2O5/C) as a potential cathode material for sodium-ion batteries (SIBs) offers significant specific capacities in energy storage systems but suffers from slow ionic diffusivity upon long cycling at higher current rates, thereby generally resulting in substandard electrochemical performance. This study suggests a facile strategy to enhance the electrochemical performance of V2O5/C as a cathode in sodium-ion batteries via titanium (Ti) doping using the pre-synthesized Ti-doped vanadium-based metal-organic framework template (V-MIL-101) as the precursor, which can be converted into a sophisticated core-shell type structure in which titania nanoparticle-based shell surrounds the vanadium oxide with a porous carbon-based octahedral core. Structural characterization reveals that Ti-doping forms a protective layer around vanadium based MIL-101 octahedrons that, upon pyrolysis, preserves the octahedral geometry and transforms into a nanoporous core-shell structure. It also greatly enhances the electrochemical performance as a cathode for SIBs. The titania-doped vanadium oxide structures represent higher specific capacities than the undoped vanadium oxide cathode, whereas among all the titania-doped samples, the 3 wt% TiO2@V2O5/C exhibited a much higher reversible capacity of 276.2 mAh/g as compared to the other cathode samples at 0.1C current rate and was able to retain a capacity of 250.1 mAh/g with a high coulombic efficiency after 200 cycles. Titanium species induce the formation of oxygen vacancies and V+5 species, which enhance the electrode's electric conductivity and ion diffusion—the stable octahedrons with a porous structure and carbon hybridisation in 3 wt% TiO2@V2O5/C could facilitate ion/electron transfer through shortened diffusion pathways.

W-based MOF derived ZnWO4/ZnO@C hierarchical nanoflakes with superior lithium storage performance

Tungstate-based materials as lithium-ion battery anodes have drawn multitudinous attention owing to their great theoretical capacity and typical multielectron transfer process. Nevertheless, their slow electrochemical reaction kinetics and big volume variation often trigger poor lithium storage properties. Herein, novel ZnWO4/ZnO@C hierarchical nanoflakes are engineered via a facile W-based metal-organic framework (W-MOF) template method. The ZnWO4/ZnO@C nanoflakes with a rectangular shape and high porosity are constructed by carbon-coated nanocrystal subunits. The unique composition and microstructure of ZnWO4/ZnO@C can shorten the pathway for Li+/electron transport, expand the contact with the electrolyte, improve the electrical conductivity, and fortify structural stability. Consequently, the ZnWO4/ZnO@C material as LIBs anodes delivers a high reversible capacity of 734 mAh g-1 after 150 cycles at 200 mA g-1, decent rate capability (426 mAh g-1 at 1000 mA g-1), and outstanding cyclic stability (93.8 % capacity retention over 350 cycles at 500 mA g-1). The in-situ XRD combined with ex-situ XPS and FT-IR was performed to elucidate the lithium storage mechanism of ZnWO4/ZnO@C. This work presents a simple and efficient approach for the synthesis of novel tungstate-based anodes for lithium-ion battery applications.

MOF-derived S-doped NiCo2O4 hollow cubic nanocage for highly efficient electrocatalytic oxygen evolution

Inducing the surface reconstruction of spinels is critical for improving the electrocatalytic oxygen evolution reaction (OER) activity. Herein, S-doped NiCo2O4 hollow cubic nanocage was synthesized by anion etching Metal-Organic Frameworks (MOFs) template and air annealing strategies. The hollow structure possesses a large specific surface area and pore size, facilitating active site exposure and mass transport. S2− doping regulates the electronic structure, reducing the oxidation potential of Ni sites during the OER process, thus promoting the surface reconstruction into γ-NiOOH active species. Meanwhile, S2− doping enhances conductivity, accelerating interfacial charge transfer. As a result, S-NiCo2O4-6 exhibits superior OER activity (262 mV overpotential @ 10 mA cm−2) and stability in 1.0 M KOH solution. Furthermore, 20 % Pt/C‖S-NiCo2O4-6 only needs 1.832 V to achieve 50 mA (the electrochemical active area is 4 cm2) in a homemade anion exchange membrane (AEM) electrolyzer. This work proposes a novel approach for preparing efficient anion-doped spinel-based OER electrocatalysts.

In situ Growth of Zeolite Imidazole Frameworks (ZIF-67) on Carbon Cloth for the Application of Oxygen Reduction Reactions and Microbial Fuel Cells.

Developing high surface area catalysts is an effective strategy to enhance the oxygen reduction reaction (ORR) in the application of microbial fuel cells (MFCs). This can be achieved by developing a catalyst based on metal-organic frameworks (MOFs) because they offer a porous active site for ORR. In this work, a novel in situ growth of 2D shell nanowires of ZIF-67 as a template for N-doped carbon (Co/NC) via a carbonization route was developed to enhance the ORR performance. The effects of different reaction times and different annealing temperatures were studied for a better ORR activity. The growth of the MOF template on the carbon cloth was confirmed using scanning electron microscopy, field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared. The Co/NC-800 exhibited an enhancement in the ORR activity as evidenced by an onset potential and half-wave potential of 0.0 vs V Ag/AgCl and -0.1 vs V Ag/AgCl, respectively, with a limited current density exceeding the commercial Pt/C. Operating Co/NC-800 on MFC revealed a maximum power density of 30 ± 2.5 mW/m2, a maximum current density of 180 ± 2.5 mA/m2.

Facile construction of ZnWO4/ZnO porous nanoplates on reduced graphene oxide for superior lithium storage

Zinc tungstate (ZnWO4) shows great promise as an anode material for lithium-ion batteries (LIBs) owing to its reversible multi-electron redox reactions and high theoretical capacity. Nevertheless, the low conductivity and big strain during cycling can lead to the inferior electrochemical properties of the ZnWO4 anode, hindering its practical application. Herein, we report a novel composite with ZnWO4/ZnO porous nanoplates in-situ constructed on reduced graphene oxide (rGO) by a metal–organic framework template strategy. The nanoplates with good porosity are composed of nanoparticles and nanorods, providing a short Li+-diffusion distance and plentiful Li+ storage active sites. The introduction of rGO can accelerate charge transfer and reinforce structural stability. As a result of these advantages, the ZnWO4/ZnO/rGO composite as LIBs anode delivers a high reversible capacity of 811 mAh g after 100 cycles at 200 mA g−1, excellent rate capability (437 mAh g at 5000 mA g−1), and good long cycling stability (485 mAh g after 500 cycles at 2000 mA g−1). Notably, the rate capability of the composite far precedes the previously reported ZnWO4-based anodes. This work provides an efficient approach for designing and fabricating advanced metal tungstate-based anodes for high-performance LIBs.

Metal organic framework template method for the preparation of bimetallic oxide CunCoOx catalysts for the catalytic oxidation of volatile organic compounds

A series of CunCoOx bimetallic oxides were synthesized by calcination of xCu/ZIF-67 precursors pre-impregnated with Cu2+. The Cu7CoOx catalyst demonstrated remarkable reactivity, reaching about 90 % conversion of toluene and ethylene at 194 °C and 162 °C. Additionally, Cu7CoOx was deemed suitable for applications at high space velocities, and also displaying superior stability. The physicochemical properties of CunCoOx were investigated by SEM, TEM, XRD, FTIR, BET, Raman, TG, O2-TPD, H2-TPR and XPS characterizations. The excellent catalytic performance of Cu7CoOx is attributed to the strong interaction of the two metal oxides, excellent redox ability, abundant lattice defects, more reactive oxygen species and higher concentrations of Co2+ and OLatt species. Density functional theory (DFT) calculation revealed CuO/Co3O4 (220) (Eads,O2 = −0.92 eV, Eads,toluene = −1.52 eV) displayed lower adsorption energy for toluene and oxygen molecules than Co3O4 (220) (Eads,O2 = −0.30 eV, Eads,toluene = −0.90 eV), which was favorable for the catalyst to catalyze the oxidation of VOCs. The possible degradation mechanism of toluene on Cu7CoOx was revealed using in situ DRIFTS. Thus, this work provides a non-noble metal catalyst with great application potential in VOCs treatment.

Metal-organic framework template-guided electrochemical lithography on substrates for SERS sensing applications

The templating method holds great promise for fabricating surface nanopatterns. To enhance the manufacturing capabilities of complex surface nanopatterns, it is important to explore new modes of the templates beyond their conventional masking and molding modes. Here, we employed the metal-organic framework (MOF) microparticles assembled monolayer films as templates for metal electrodeposition and revealed a previously unidentified guiding growth mode enabling the precise growth of metallic films exclusively underneath the MOF microparticles. The guiding growth mode was induced by the fast ion transportation within the nanochannels of the MOF templates. The MOF template could be repeatedly used, allowing for the creation of identical metallic surface nanopatterns for multiple times on different substrates. The MOF template-guided electrochemical growth mode provided a robust route towards cost-effective fabrication of complex metallic surface nanopatterns with promising applications in metamaterials, plasmonics, and surface-enhanced Raman spectroscopy (SERS) sensing fields.

MOF-Derived Copper Selenides Implanted in Octahedral Carbon Matrix for Efficient Hydrogen Evolution Reaction

The development of durable, efficient catalysts is vital in electrochemical water dissociation. Metal-organic frameworks (MOFs) based nanomaterials have been explored due to their well-distribution metal nodes and stability, but the shortage of efficient cathode compounds for electrochemical hydrogen evolving restricted their industrial applications. Herein, Cu2Se nanocrystals embedded in the octahedral carbon frameworks (Cu2Se/C) were fabricated using a copper-related MOF template through a one-step selenization technique. Interestingly, the catalytic efficacy of Cu2Se/C is better than that of Cu/C and Cu-MOF as catalysts for hydrogen generation in an acidic medium. In particular, Cu2Se/C shows a moderate overpotential of 220 mV at a current density of 10 mA cm−2 and a low Tafel slope of 54.5 mV dec−1. Also, this catalyst presents outstanding durability with 2000 cycling operations and 12 h of testing by chronoamperometry. The high efficiency is assigned to the synergistic effect of Cu2Se nanoparticles and carbon frameworks, which play essential roles in increasing exposed catalytic sites and protected active centers. The results may open potential direction to prepare economical hydrogen-evolving electrocatalysts.

Facial synthesis of core-shell nickel@carbon nanocomposite for high-efficient electrochemical detection of paracetamol

Nickel nanoparticles (Ni NPs) are attracting more and more attention in the field of electrochemistry due to their high conductivity and good catalytic properties. However, Ni NPs are susceptible to corrosion or agglomeration, leading to low stability. In this work, nickel@carbon nanomaterials (Ni@CNS) were prepared by pyrolysis nickel-based metal-organic framework (Ni-MOF) template, and characterized by powder X-ray diffraction (PXRD), transmission electron microscopy, scanning electron microscopy, Brunauer–Emmett–Teller method, and X-ray photoelectron spectroscopy (XPS). The prepared Ni@CNS composite reveals uniform core-shell structure, where the thin carbon shell not only protects the Ni NPs from being corroded, but also accelerates the migration of electrons, so as to promote its sensing performance. Ni@CNS composite presented as a black powder with mesoporous structure. The average size of Ni NPs was about 15.01 nm with a standard deviation of 3.21 nm. The specific surface area of Ni@CNS was as high as 116.12 m2 g[Formula: see text], which is beneficial to increase the effective surface area of the modified electrode. These structural advantages enhance its electrochemical performance toward paracetamol (PA) sensing. The Ni@CNS modified electrode has high sensitivity for quantitative detection of PA. The linear ranges were determined to be 0.570 [Formula: see text]M and 70432 [Formula: see text]M with a low detection limit of 0.028 [Formula: see text]M ([Formula: see text]/[Formula: see text] = 3). In addition, due to its excellent electrochemical performances, the constructed electrode was used to detect PA in real water samples. This work expands the application of Ni- and C-based composites in electrochemistry sensing.

Tuning the electrochemical behaviors of N-doped LiMnxFe1–xPO4/C via cation engineering with metal-organic framework-templated strategy

LiFePO4, as a prevailing cathode material for lithium-ion batteries (LIBs), still encounters issues such as intrinsic poor electronic conductivity, inferior Li-ion diffusion kinetic, and two-phase transformation mechanism involving substantial structural rearrangements, resulting in unsatisfactory rate performance. Carbon coating, cation doping, and morphological control have been widely employed to reconcile these issues. Inspired by these, we propose a synthetic route with metal–organic frameworks (MOFs) as self-sacrificial templates to simultaneously realize shape modulation, Mn doping, and N-doped carbon coating for enhanced electrochemical performances. The as-synthesized LiMnxFe1–xPO4/C (x = 0, 0.25, and 0.5) deliver tunable electrochemical behaviors induced by the MOF templates, among which LiMn0.25Fe0.75PO4/C outperforms its counterparts in cyclability (164.7 mA h g−1 after 200 cycles at 0.5 C) and rate capability (116.3 mA h g−1 at 10 C). Meanwhile, the ex-situ XRD reveals a dominant single-phase solid solution mechanism of LiMn0.25Fe0.75PO4/C during delithiation, contrary to the pristine LiFePO4, without major structural reconstruction, which helps to explain the superior rate performance. Furthermore, the density functional theory (DFT) calculations verify the effects of Mn doping and embody the superiority of LiMn0.25Fe0.75PO4/C as a LIB cathode, which well supports the experimental observations. This work provides insightful guidance for the design of tunable MOF-derived mixed transition-metal systems for advanced LIBs.

Improved performance of fiber-optic hydrogen sensor of porous Pt/WO3 based on ZIF-8

A novel fiber-optic hydrogen sensor including Pt/WO3 sensing material with a microporous structure is proposed and experimentally demonstrated with improved performance. The proposed Pt/WO3 sensing material is realized by introducing metal-organic frameworks (MOFs) as templates. The mesoporous structure of the ZIF-8 template improves the reactive sites of hydrogen sensitive materials with hydrogen. Hydrogen sensors were fabricated by combining the synthesized material with Fiber Bragg Gratings (FBGs) and the performance of hydrogen sensors was investigated. The experimental results show that the hydrogen sensitivity of the FBG with ZIF-8 synthesized Pt/WO3 has been increased to 0.075 pm/ppm, which is twice that without ZIF-8 synthetization. The stability and the response speed are also significantly improved. The introduction of microporous MOFs templates into Pt/WO3 sensing material will greatly accelerate the wide application of Pt/WO3-based fiber optic hydrogen sensors on hydrogen leakage detection.

Hierarchical Cube-in-Cube Cobalt-Molybdenum Phosphide Hollow Nanoboxes Derived from the MOF Template Strategy for High-Performance Supercapacitors.

The design of hierarchical hollow nanostructures with complex shell architectures is an attractive and effective way to obtain a desirable electrode material for energy storage application. Herein, we report an effective metal-organic framework (MOF) template-engaged method to synthesize novel double-shelled hollow nanoboxes, in terms of chemical composition and structure complexity, for supercapacitor application. Starting from cobalt-based zeolitic imidazolate framework (ZIF-67(Co)) nanoboxes as the removal template, we developed a rational preparation approach to synthesize cobalt-molybdenum-phosphide (CoMoP) double-shelled hollow nanoboxes (donated as CoMoP-DSHNBs) through (i) ion-exchange reaction, (ii) template etching, and (iii) phosphorization treatment, respectively. Notably, despite the previously reported works, the phosphorization was simply done using the facile solvothermal method, without employing annealing and high-temperature conditions, which can be considered as one of the merits of the current work. CoMoP-DSHNBs showed excellent electrochemical properties owing to their unique morphology, high surface area, and optimal elemental composition. In a three-electrode system, the target material showed a superior specific capacity of 1204 F g-1 at 1 A g-1 with a remarkable cycle stability of 87% after 20000 cycles. The hybrid device formed of activated carbon (AC) as the negative electrode and CoMoP-DSHNBs as the positive electrode exhibited a high specific energy density of 49.99 W h kg-1 and a maximum power density of 7539.41 W kg-1 with a great cycling stability of 84.5% after 20,000 cycles.

Effect of a Zr-Based Metal-Organic Framework Structure on the Properties of Its Composite with Polyaniline.

Composites of polyaniline (PANI) and Zr-based metal-organic frameworks (MOFs), UiO-66 and UiO-66-NH2, were synthesized by the oxidative polymerization of aniline in the presence of MOF templates with the MOF content in the resulting materials (78.2 and 86.7 wt %, respectively) close to the theoretical value (91.5 wt %). Scanning electron microscopy and transmission electron microscopy showed that the morphology of the composites was set by the morphology of the MOFs, whose structure was mostly preserved after the synthesis, based on the X-ray diffraction data. Vibrational and NMR spectroscopies pointed out that MOFs participate in the protonation of PANI and conducting polymer chains were grafted to amino groups of UiO-66-NH2. Unlike PANI-UiO-66, cyclic voltammograms of PANI-UiO-66-NH2 showed a well-resolved redox peak at around ≈0 V, pointing at the pseudocapacitive behavior. The gravimetric capacitance of PANI-UiO-66-NH2, normalized per mass of the active material, was also found to be higher compared to that of pristine PANI (79.8 and 50.5 F g-1, respectively, at 5 mV s-1). The introduction of MOFs into the composites with PANI significantly improved the cycling stability of the materials over 1000 cycles compared to the pristine conducting polymer, with the residual gravimetric capacitance being ≥100 and 77%, respectively. Thus, the electrochemical performance of the prepared PANI-MOF composites makes them attractive materials for application in energy storage.