Accelerating Oxygen Electrocatalysis Kinetics on Metal-Organic Frameworks via Bond Length Optimization

Metal-organic frameworks(MOFs)have been developed as an ideal platform for exploration of the relationship between intrinsic structure and catalytic activity,but the limited catalytic activity and stability has hampered their practical use in water splitting.Herein,we develop a bond length adjustment strategy for optimizing naphthalene-based MOFs that synthesized by acid etching Co-naphthalenedicarboxylic acid-based MOFs(donated as AE-CoNDA)to serve as efficient catalyst for water splitting.AE-CoNDA exhibits a low overpotential of 260 mV to reach 10 mA cm^(−2)and a small Tafel slope of 62 mV dec^(−1)with excellent stability over 100 h.After integrated AE-CoNDA onto BiVO_(4),photocurrent density of 4.3 mA cm^(−2)is achieved at 1.23 V.Experimental investigations demonstrate that the stretched Co-O bond length was found to optimize the orbitals hybridization of Co 3d and O 2p,which accounts for the fast kinetics and high activity.Theoretical calculations reveal that the stretched Co-O bond length strengthens the adsorption of oxygen-contained intermediates at the Co active sites for highly efficient water splitting.

Metal-organic frameworks and their composites for advanced lithium-ion batteries:Synthesis,progress and prospects

Metal-organic frameworks(MOFs)are among the most promising materials for lithium-ion batteries(LIBs)owing to their high surface area,periodic porosity,adjustable pore size,and controllable chemical composition.For instance,their unique porous structures promote electrolyte penetration,ions transport,and make them ideal for battery separators.Regulating the chemical composition of MOF can introduce more active sites for electrochemical reactions.Therefore,MOFs and their related composites have been extensively and thoroughly explored for LIBs.However,the reported reviews solely include the applications of MOFs in the electrode materials of LIBs and rarely involve other aspects.A systematic review of the application of MOFs in LIBs is essential for understanding the mechanism of MOFs and better designing related MOFs battery materials.This review systematically evaluates the latest developments in pristine MOFs and MOF composites for LIB applications,including MOFs as the main materials(anode,cathode,separators,and electrolytes)to auxiliary materials(coating layers and additives for electrodes).Furthermore,the synthesis,modification methods,challenges,and prospects for the application of MOFs in LIBs are discussed.

Synergistic catalysis of the N-hydroxyphthalimide on flower-like bimetallic metal-organic frameworks for boosting oxidative desulfurization

Synergic catalytic effect between active sites and supports greatly determines the catalytic activity for the aerobic oxidative desulfurization of fuel oils.In this work,Ni-doped Co-based bimetallic metal-organic framework(CoNi-MOF)is fabricated to disperse N-hydroxyphthalimide(NHPI),in which the whole catalyst provides plentiful synergic catalytic effect to improve the performance of oxidative desulfurization(ODS).As a bimetallic MOF,the second metal Ni doping results in the flower-like morphology and the modification of electronic properties,which ensure the exposure of NHPI and strengthen the synergistic effect of the overall catalyst.Compared with the monometallic Co-MOF and naked NHPI,the NHPI@CoNi-MOF triggers the efficient activation of molecular oxygen and improves the ODS performance without an initiator.The sulfur removal of dibenzothiophene-based model oil reaches 96.4%over the NHPI@CoNi-MOF catalyst in 8 h of reaction.Furthermore,the catalytic product of this aerobic ODS reaction is sulfone,which is adsorbed on the catalyst surface due to the difference in polarity.This work provides new insight and strategy for the design of a strong synergic catalytic effect between NHPI and bimetallic supports toward high-activity aerobic ODS materials.

Hollow Metal-Organic Framework/MXene/Nanocellulose Composite Films for Giga/Terahertz Electromagnetic Shielding and Photothermal Conversion

With the continuous advancement of communication technology,the escalating demand for electromagnetic shielding interference(EMI)materials with multifunctional and wideband EMI performance has become urgent.Controlling the electrical and magnetic components and designing the EMI material structure have attracted extensive interest,but remain a huge challenge.Herein,we reported the alternating electromagnetic structure composite films composed of hollow metal-organic frameworks/layered MXene/nanocellulose(HMN)by alternating vacuum-assisted filtration process.The HMN composite films exhibit excellent EMI shielding effectiveness performance in the GHz frequency(66.8 dB at Kaband)and THz frequency(114.6 dB at 0.1-4.0 THz).Besides,the HMN composite films also exhibit a high reflection loss of 39.7 dB at 0.7 THz with an effective absorption bandwidth up to 2.1 THz.Moreover,HMN composite films show remarkable photothermal conversion performance,which can reach 104.6℃under 2.0 Sun and 235.4℃under 0.8 W cm^(−2),respectively.The unique micro-and macrostructural design structures will absorb more incident electromagnetic waves via interfacial polarization/multiple scattering and produce more heat energy via the local surface plasmon resonance effect.These features make the HMN composite film a promising candidate for advanced EMI devices for future 6G communication and the protection of electronic equipment in cold environments.

Temperature-feedback two-photon-responsive metal-organic frameworks for efficient photothermal therapy

The realization of real-time thermal feedback for monitoring photothermal therapy(PTT)under near-infrared(NIR)light irradiation is of great interest and challenge for antitumor therapy.Herein,by assembling highly efficient photothermal conversion gold nanorods and a temperature-responsive probe((E)-4-(4-(diethylamino)styryl)-1-methylpyridin-1-ium,PyS)within MOF-199,an intelligent nanoplatform(AMPP)was fabricated for simultaneous chemodynamic therapy and NIR light-induced temperature-feedback PTT.The fluorescence intensity and temperature of the PyS probe are linearly related due to the restriction of the rotation of the characteristic monomethine bridge.Moreover,the copper ions resulting from the degradation of MOF-199 in an acidic microenvironment can convert H_(2)O_(2)into•OH,resulting in tumor ablation through a Fenton-like reaction,and this process can be accelerated by increasing the temperature.This study establishes a feasible platform for fabricating highly sensitive temperature sensors for efficient temperature-feedback PTT.

Photophysics of metal-organic frameworks:A brief overview

Metal-organic frameworks(MOFs),which are self-assembled porous coordination materials,have garnered considerable attention in the fields of optoelectronics,photovoltaic,photochemistry,and photocatalysis due to their diverse structures and excellent tunability.However,the performance of MOF-based optoelectronic applications currently falls short of the industry benchmark.To enhance the performance of MOF materials,it is imperative to undertake comprehensive investigations aimed at gaining a deeper understanding of photophysics and sequentially optimizing properties related to photocarrier transport,recombination,interaction,and transfer.By utilizing femtosecond laser pulses to excite MOFs,time-resolved optical spectroscopy offers a means to observe and characterize these ultrafast microscopic processes.This approach adds the time coordinate as a novel dimension for comprehending the interaction between light and MOFs.Accordingly,this review provides a comprehensive overview of the recent advancements in the photophysics of MOFs and additionally outlines potential avenues for exploring the time domain in the investigation of MOFs.

Metal-organic-framework-derived copper-based catalyst for multicomponent C-S coupling reaction

Copper-based metal-organic frameworks(Cu-MOFs)are a promising multiphase catalyst for catalyzing C-S coupling reactions by virtue of their diverse structures and functions.However,the unpleasant odor and instability of the organosulfur,as well as the mass-transfer resistance that exists in multiphase catalysis,have often limited the catalytic application of Cu-MOFs in C-S coupling reactions.In this paper,a Cu-MOFs catalyst modified by cetyltrimethylammonium bromide(CTAB)was designed to enhance mass transfer by increasing the adsorption of organic substrates using the long alkanes of CTAB.Concurrently,elemental sulfur was used to replace organosulfur to achieve a highly efficient and atom-economical multicomponent C-S coupling reaction.

Regulating interfacial behavior of zinc metal anode via metal-organic framework functionalized separator

Aqueous zinc ion batteries(AZIBs)are one of the promising energy storage devices.However,uncontrolled dendrite and side reactions have seriously hindered its further application.In this study,the metal-organic framework(MOF)functionalized glass fiber separator(GF-PFC-31)was used to regulate interfacial behavior of zinc metal anode,enabling the development of high-performance AZIBs.In PFC-31,there areπ-πinteractions between two adjacent benzene rings with a spacing of 3.199 A.This spacing can block the passage of[Zn(H_(2)O)_6]^(2+)(8.6 A in diameter)through the GF-PFC-31 separator to a certain extent,which promotes the deposition process of Zn ions.In addition,the sulfonic acid group(-S03H)contained in GF-PFC-31 can form a hydrogen bonding network with H_(2)O,which can provide a desolvation effect and reduce the side reaction.Consequently,GF-PFC-31 separator achieves uniform deposition of Zn ions.The Zn‖GF-PFC-31‖Zn symmetric cell exhibits stable cycle life(3000 h at 1.2 mA cm^(-2),2000 h at 0.3 mA cm^(-2),and 2000 h at 5.0 mA cm^(-2)),and Zn‖GF-PFC-31‖MnO_(2) full cell with GF-PFC-31 separator can cycle for 1000 cycles at 1.2 A g^(-1)with capacity retention rate of 82.5%.This work provides a promising method to achieve high-performance AZIBs.

Metal-organic framework-derived porous carbon for the advanced aqueous zinc-ion hybrid capacitor

Aqueous zinc ion hybrid capacitors(ZIHCs)are considered one of the most promising electrochemical energy storage systems due to their high safety,environmental friendliness,low cost,and high power density.However,the low energy density and the lack of sustainable design strategies for the cathodes hinder the practical application of ZIHCs.Herein,we design the N and O co-doped porous carbon cathode by annealing metal-organic framework(ZIF-8).ZIF-8 retains the original dodecahedral structure with a high specific surface(2814.67 m^(2)/g)and I_(G)/I_(D) ratio of 1.0 during carbonization and achieves self-doping of N and O heteroatoms.Abundant defect sites are introduced into the porous carbon to provide additional active sites for ion adsorption after the activation of carbonized ZIF-8 by KOH treatment.The ZIHCs assembled with modified ZIF-8 as the cathode and commercial zinc foil as the anode show an energy density of 125 W∙h/kg and a power density of 79 W/kg.In addition,this ZIHCs device achieves capacity retention of 77.8%after 9000 electrochemical cycles,which is attributed to the diverse pore structure and plentiful defect sites of ZIF-8-800(KOH).The proposed strategy may be useful in developing high-performance metal-ion hybrid capacitors for large-scale energy storage.

Improvement of ionic conductivity of solid polymer electrolyte based on Cu-Al bimetallic metal-organic framework fabricated through molecular grafting

A composite solid electrolyte comprising a Cu-Al bimetallic metal-organic framework(CAB),lithium salt(LiTFSI)and polyethylene oxide(PEO)was fabricated through molecular grafting to enhance the ionic conductivity of the PEO-based electrolytes.Experimental and molecular dynamics simulation results indicated that the electrolyte with 10 wt.%CAB(PL-CAB-10%)exhibits high ionic conductivity(8.42×10~(-4)S/cm at 60℃),high Li+transference number(0.46),wide electrochemical window(4.91 V),good thermal stability,and outstanding mechanical properties.Furthermore,PL-CAB-10%exhibits excellent cycle stability in both Li-Li symmetric battery and Li/PL-CAB-10%/LiFePO4 asymmetric battery setups.These enhanced performances are primarily attributable to the introduction of the versatile CAB.The abundant metal sites in CAB can react with TFSI~-and PEO through Lewis acid-base interactions,promoting LiTFSI dissociation and improving ionic conductivity.Additionally,regular pores in CAB provide uniformly distributed sites for cation plating during cycling.

Engineering Spin States of Isolated Copper Species in a Metal-Organic Framework Improves Urea Electrosynthesis

The catalytic activities are generally believed to be relevant to the electronic states of their active center, but understanding this relationship is usually difficult. Here, we design two types of catalysts for electrocatalytic urea via a coordination strategy in a metal–organic frameworks: Cu^(Ⅲ)-HHTP and Cu^(Ⅱ)-HHTP. Cu^(Ⅲ)-HHTP exhibits an improved urea production rate of 7.78 mmol h^(−1)g^(−1) and an enhanced Faradaic efficiency of 23.09% at-0.6 V vs. reversible hydrogen electrode, in sharp contrast to Cu^(Ⅱ)-HHTP.Isolated CuⅢspecies with S = 0 spin ground state are demonstrated as the active center in Cu^(Ⅲ)-HHTP, different from Cu^(Ⅱ) with S = 1/2 in Cu^(Ⅱ)-HHTP. We further demonstrate that isolated Cu^(Ⅲ)with an empty dx2-y20orbital in Cu^(Ⅲ)-HHTP experiences a single-electron migration path with a lower energy barrier in the C–N coupling process, while Cu^(Ⅱ)with a single-spin state( d_(x2-y2)^(1)) in Cu^(Ⅱ)-HHTP undergoes a two-electron migration pathway.

Dual-conductive metal-organic framework@MXene heterogeneity stabilizes lithium-ion storage

Although a few pristine metal-organic frameworks(MOFs) of graphene analogue topology exhibit high intrinsic electrical conductivity, their use in lithium-ion batteries(LIBs) is still hampered by unfavorable Li+adsorption energy(ΔEa). In this paper, an electroconductive ferrocene-based MOF@MXene heterostructure is built to provide stable anodes for Li+storage. Charge density difference and planar average potential charge density show substantial redistribution of charges at the interfaces, transferring from MXene to MOF layers. Moreover, density functional theory(DFT) calculations reveal that the interaction between MXene and MOF significantly increases the ΔEa. As a result, the heterostructure anode exhibits high capacities and outstanding cycling stability with a capacity retention of 80% after 5000 cycles at 5 A g^(-1), outperforming mono-component MXene and MOF. Furthermore, the heterostructure anode is built into a full cell with a commercial NCM 532 cathode, delivering a high energy density of 611 Wh kg^(-1)and power density of 7600 W kg^(-1). The developed conductive MOF@MXene heterogeneity for improved LIB offers valuable insights into the design of advanced electrode materials for energy storage.

Tuning the electronic structure of a metal-organic framework for an efficient oxygen evolution reaction by introducing minor atomically dispersed ruthenium

The establishment of efficient oxygen evolution electrocatalysts is of great value but also challenging.Herein,a durable metal–organic framework(MOF)with minor atomically dispersed ruthenium and an optimized electronic structure is constructed as an efficient electrocatalyst.Significantly,the obtained NiRu_(0.08)-MOF with doping Ru only needs an overpotential of 187 mV at 10 mA cm^(-2) with a Tafel slop of 40 mV dec^(-1) in 0.1M KOH for the oxygen evolution reaction,and can work continuously for more than 300 h.Ultrahigh Ru mass activity is achieved,reaching 56.7 Ag^(-1)_(Ru) at an overpotential of 200 mV,which is 36 times higher than that of commercial RuO_(2).X-ray adsorption spectroscopy and density function theory calculations reveal that atomically dispersed ruthenium on metal sites in MOFs is expected to optimize the electronic structure of nickel sites,thus improving the conductivity of the catalyst and optimizing the adsorption energy of intermediates,resulting in significant optimization of electrocatalytic performance.This study could provide a new avenue for the design of efficient and stable MOF electrocatalysts.

Research progress on the substrate for metal-organic framework(MOF) membrane growth for separation

During the last decade, metal-organic frameworks(MOFs) have been applied in various fields due to their unique chemical and functional advantages. One of the widespread research hotspots is MOF-based membranes for separations, specifically continuous defect-free MOF membranes, which are usually grown on porous substrates. The substrate not only serves as the MOF layer support but also has a great influence on the membrane fabrication process and the final separation performance of the resultant membrane. In this review, we mainly introduce the progress focused on the substrates for MOF membranes fabrication. The substrate modifications and seeding methods aimed at synthesizing highquality MOF membranes are also summarized systematically.

Structural survey of metal-covalent organic frameworks and covalent metal-organic frameworks

This review offers an overview of the latest developments in metal-covalent organic framework(MCOF)and covalent metal-organic framework(CMOF)materials,whose construction entails a combination of reversible coordination and covalent bonding adapted from metal-organic frameworks(MOFs)and covalent organic frameworks(COFs),respectively.With an emphasis on the MCOF and CMOF structures,this review surveys their building blocks and topologies.Specifically,the frameworks are classified based on the dimensions of their components(building blocks),namely,discrete building blocks and one-dimensional infinite building blocks.For the first category,the materials are further divided into collections of two-and three-dimensional networks based on their topologies.For the second category,the recently emerging MCOFs with woven structures are covered.Finally,the state-of-the-art in MCOF and CMOF chemistry has been laid out for promising avenues in future developments.

Interfacial Engineering of Defect-Rich and Multi-Heteroatom-Doped Metal-Organic Framework-Derived Manganese Fluoride Anodes to Boost Lithium Storage

Manganese fluoride(MnF2)is a high-performance lithium-ion battery anode material with an excellent structural stability,low synthesis cost,and better manufacturing convenience.However,its low theoretical capacity(577 mAh g^(-1)),weak conductivity of fluoride,and poor recyclability limit its practical application.Fortunately,oxygen vacancies(Ov)and heteroatomic doping are among the most promising strategies to modulate the inherent reduced electronic conductivity and kinetic response of electrode materials in order to boost their lithium storage capacity.Herein,self-templating,self-optimizing,and self-supporting metal-organic framework template approach with the introduction of oxygen vacancies by substitution of exogenous heteroatoms is proposed,where triple heteroatom-doped(N,O,and F)carbon-encapsulated MOF-derived manganese fluoride(Ov-ZMF@NOFs)microstructures are designed.Interestingly,the exogenously introduced triple heteroatomic carbon matrix forms a fluffy three-dimensional mechanical structure,interlaced conducting networks,efficient conducting pathways,and intense electrochemical dynamics at the periphery of the manganese fluoride nanoparticles.Benefiting from the above-mentioned features,the Ov-ZMF@NOFs exhibit expected electrochemical properties with ultra-long recyclability(high reversible capacity of 419 mAh g^(-1)at 6 A g^(-1))and good rate performance(capacity of 232 mAh g^(-1)at a current density of 16 A g^(-1)).Theoretical calculations underline the essential contribution of multiple heteroatoms doping in boosting the electrode conductivity and reducing the lithium-ion migration energy barrier.Combining controllable vacancy engineering and heteroatom doping technology at the nanoscale provides a new philosophy and concept for the design and fabrication of next-generation high-energy lithium-ion battery materials.

Zinc-Based Metal-Organic Frameworks for High-Performance Supercapacitor Electrodes:Mechanism Underlying Pore Generation

Heat treatment of metal-organic frameworks(MOFs)has provided a wide variety of functional carbons coordinated with metal compounds.In this study,two kinds of zinc-based MOF(ZMOF),C_(16)H_(10)O_(4)Zn(ZMOF1)and C_(8)H_(4)O_(4)Zn(ZMOF2),were prepared.ZMOF1 and ZMOF2 were carbonized at 1000℃,forming CZMOF1 and CZMOF2,respectively.The specific surface area(S_(BET))of CZMOF2 was~2700 m^(2)g^(−1),much higher than that of CZMOF1(~1300 m^(2)g^(−1)).A supercapacitor electrode based on CZMOF2 achieved specific capacitances of 360,278,and 221 F g^(−1)at 50,250,and 1000 mA g^(−1)in an aqueous electrolyte(H2SO_(4)),respectively,the highest values reported to date for ZMOF-derived electrodes under identical conditions.The practical applicability of the CZMOF-based supercapacitor was verified in non-aqueous electrolytes.The initial capacitance retention was 78%after 100000 charge/discharge cycles at 10 A g^(−1).Crucially,the high capacitance of CZMOF2 arises from pore generation during carbonization.Below 1000℃,pore generation is dominated by the Zn/C ratio of ZMOFs,as carbon atoms reduce the zinc oxides formed during carbonization.Above 1000℃,a high O/C ratio becomes essential for pore generation because the oxygen functional groups are pyrolyzed.These findings will provide insightful information for other metal-based MOFderived multifunctional carbons.

Novel in-capsule synthesis of metal-organic framework for innovative carbon dioxide capture system

Metal-Organic Frameworks(MOFs)have been developed as solid sorbents for CO_(2) capture applications and their properties can be controlled by tuning the chemical blocks of their crystalline units.A number of MOFs(e.g.,HKUST-1)have been developed but the question remains how to deploy them for gas-solid contact.Unfortunately,the direct use of MOFs as nanocrystals would lead to serious problems and risks.Here,for the first time,we report a novel MOF-based hybrid sorbent that is produced via an innovative in-situ microencapsulated synthesis.Using a custom-made double capillary microfluidic assembly,double emulsions of the MOF precursor solutions and UV-curable silicone shell fluid are produced.Subsequently,HKUST-1 MOF is successfully synthesized within the droplets enclosed in the gas permeable microcapsules.The developed MOF-bearing microcapsules uniquely allow the deployment of functional nanocrystals without the challenge of handling ultrafine particles,and further,can selectively reject undesired compounds to protect encapsulated MOFs.

Tuning the electrochemical behaviors of N-doped LiMn_(x)Fe_(1–x)PO_(4)/C via cation engineering with metal-organic framework-templated strategy

LiFePO_(4),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 Li MnxFe1–xPO4/C(x=0,0.25,and0.5)deliver tunable electrochemical behaviors induced by the MOF templates,among which LiMn_(0.25)Fe_(0.75)PO_(4)/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 LiMn_(0.25)Fe_(0.75)PO_(4)/C during delithiation,contrary to the pristine LiFePO_(4),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 LiMn_(0.25)Fe_(0.75)PO_(4)/C as a LIB cathode,which well supports the experimental observations.This work provides insightful guidance for the design of tunable MOF-derived mixed transitionmetal systems for advanced LIBs.

Laminar Composite Solid Electrolyte with Poly(Ethylene Oxide)-Threaded Metal-Organic Framework Nanosheets for High-Performance All-Solid-State Lithium Battery

Developing laminar composite solid electrolyte with ultrathin thickness and continuous conduction channels in vertical direction holds great promise for all-solid-state lithium batteries.Herein,a thin,laminar solid electrolyte is synthesized by filtrating–NH 2 functionalized metal-organic framework nanosheets and then being threaded with poly(ethylene oxide)chains induced by the hydrogen-bonding interaction from–NH_(2) groups.It is demonstrated that the threaded poly(ethylene oxide)chains lock the adjacent metal-organic framework nanosheets,giving highly enhanced structural stability(Young’s modulus,1.3 GPa)to 7.5-μm-thick laminar composite solid electrolyte.Importantly,these poly(ethylene oxide)chains with stretching structure serve as continuous conduction pathways along the chains in pores.It makes the non-conduction laminar metal-organic framework electrolyte highly conductive:3.97×10^(−5) S cm^(−1) at 25℃,which is even over 25 times higher than that of pure poly(ethylene oxide)electrolyte.The assembled lithium cell,thus,acquires superior cycling stability,initial discharge capacity(148 mAh g^(−1) at 0.5 C and 60℃),and retention(94% after 150 cycles).Besides,the pore size of nanosheet is tailored(24.5–40.9˚A)to evaluate the mechanisms of chain conformation and ion transport in confined space.It shows that the confined pore only with proper size could facilitate the stretching of poly(ethylene oxide)chains,and meanwhile inhibit their disorder degree.Specifically,the pore size of 33.8˚A shows optimized confinement effect with trans-poly(ethylene oxide)and cis-poly(ethylene oxide)conformation,which offers great significance in ion conduction.Our design of poly(ethylene oxide)-threaded architecture provides a platform and paves a way to the rational design of next-generation high-performance porous electrolytes.