Dipole polarization modulating of vinylene-linked covalent organic frameworks for efficient photocatalytic hydrogen evolution

Photocatalytic hydrogen(H_(2))evolution using covalent organic frameworks(COFs)is an attractive and promising avenue for exploration,but one of its big challenges is low photo-induced charge separation.In this study,we present a straightforward and facile dipole polarization engineering strategy to enhance charge separation efficiency,achieved through atomic modulation(O,S,and Se)of the COF monomer.Our findings demonstrate that incorporating atoms with varying electronegativities into the COF matrix significantly influences the local dipole moment,thereby affecting charge separation efficiency and photostability,which in turn affects the rates of photocatalytic H_(2) evolution.As a result,the newly developed TMT-BO-COF,which contains highly electronegative O atoms,exhibits the lowest exciton binding energy,the highest efficiency in charge separation and transportation,and the longest lifetime of the active charges.This leads to an impressive average H_(2) production rate of 23.7 mmol g^(−1) h^(−1),which is 2.5 and 24.5 times higher than that of TMT-BS-COF(containing S atoms)and TMT-BSe-COF(containing Se atoms),respectively.A novel photocatalytic hydrogen evolution mechanism based on proton-coupled electron transfer on N in the structure of triazine rings in vinylene-linked COFs is proposed by theoretical calculations.Our findings provide new insights into the design of highly photoactive organic framework materials for H_(2) evolution and beyond.

Superposition of dual electric fields in covalent organic frameworks for efficient photocatalytic hydrogen evolution

Covalent organic frameworks(COFs)are promising materials for converting solar energy into green hydrogen.However,limited charge separation and transport in COFs impede their application in the photocatalytic hydrogen evolution reaction(HER).In this study,the intrinsically tunable internal bond electric field(IBEF)at the imine bonds of COFs was manipulated to cooperate with the internal molecular electric field(IMEF)induced by the donor-acceptor(D-A)structure for an efficient HER.The aligned orientation of IBEF and IMEF resulted in a remarkable H_(2) evolution rate of 57.3 mmol·g^(-1)·h^(-1)on TNCA,which was approximately 520 times higher than that of TCNA(0.11 mmol·g^(-1)·h^(-1))with the opposing electric field orientation.The superposition of the dual electric fields enables the IBEF to function as an accelerating field for electron transfer,kinetically facilitat-ing the migration of photogenerated electrons from D to A.Furthermore,theoretical calculations indicate that the inhomogeneous charge distribution at the C and N atoms in TNCA not only pro-vides a strong driving force for carrier transfer but also effectively hinders the return of free elec-trons to the valence band,improving the utilization of photoelectrons.This strategy of fabricating dual electric fields in COFs offers a novel approach to designing photocatalysts for clean energy synthesis.

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.

Charge-transfer-regulated bimetal ferrocene-based organic frameworks for promoting electrocatalytic oxygen evolution

The ferrocene(Fc)-based metal-organic frameworks(MOFs)are regarded as compelling platforms for the construction of efficient and robust oxygen evolution reaction(OER)electrocatalysts due to their superior conductivity and flexible electronic structure.Herein,density functional theory simulations were addressed to predict the electronic structure regulations of CoFc-MOF by nickel doping,which demonstrated that the well-proposed CoNiFc-MOFs delivered a small energy barrier,promoted conductivity,and well-regulated d-band center.Inspired by these,a series of sea-urchin-like CoNiFc-MOFs were successfully synthesized via a facile solvothermal method.Moreover,the synchrotron X-ray and X-ray photoelectron spectroscopy measurements manifested that the introduction of nickel could tailor the electronic structure of the catalyst and induce the directional transfer of electrons,thus optimizing the rate-determining step of^(*)O→^(*)OOH during the OER process and yielding decent overpotentials of 209 and 252 mV at 10 and 200 mA cm^(−2),respectively,with a small Tafel slope of 39 mV dec^(−1).This work presents a new paradigm for developing highly efficient and durable MOF-based electrocatalysts for OER.

In situ formation of amorphous Fe-based bimetallic hydroxides from metal-organic frameworks as efficient oxygen evolution catalysts

Oxygen evolution from water driven by electrocatalysis or photocatalysis poses a significant challenge as it requires the use of efficient electro-/photo-catalysts to drive the four-electron oxygen evolution reaction(OER).Herein,we report the development of an effective strategy for the in situ chemical transformation of Fe-based bimetallic MIL-88 metal-organic frameworks(MOFs)into corresponding bimetallic hydroxides,which are composed of amorphous ultrasmall nanoparticles and afford an abundance of catalytically active sites.Optimized MOF-derived NiFe-OH-0.75 catalyst coated on glassy carbon electrodes achieved a current density of 10 mA cm^(-2)in the electrocatalytic OER with a small overpotential of 270 mV,which could be decreased to 235 mV when loading the catalysts on a nickel foam substrate.Moreover,these MOF-derived Fe-based bimetallic hydroxides can be used as efficient cocatalysts when combined with suitable photosensitizers for photocatalytic water oxidation.

Recent Progress of Metal Organic Frameworks-Based Electrocatalysts for Hydrogen Evolution,Oxygen Evolution,and Oxygen Reduction Reaction

Exploring efficient and cost-saving electrocatalysts is essential to the renewable energy storage and utilization,which is still in its embryonic period.MOFs have drawn tremendous attention due to their adjustability,abundant active sites,and plentiful pores.Notably,satisfactory electrocatalytic performance has been achieved by MOFs-based electrocatalysts comparable to traditional electrocatalysts.State-of-the-art works about the MOFs-based electrocatalysts for hydrogen evolution reaction(HER),oxygen evolution reaction(OER),and ORR were summarized in this review.This review comprises a series of modifying strategies of MOFs and their derivatives,from aspects of structure,composition,and morphology.Furthermore,the active sites and functional mechanisms’recognition are involved in this review expecting to provide reference for rationally designing efficient electrocatalysts.At last,the current status,challenges,and perspectives of MOFs-based electrocatalysts are also discussed.

Metal‐organic frameworks‐derived novel nanostructured electrocatalysts for oxygen evolution reaction

Engineering cost‐effective catalysts with exceptional performance for theelectrochemical oxygen evolution reaction (OER) remains crucial for theaccelerated development of renewable energy techniques, and especially so,given the pivotal role of OER in water electrolysis. On the basis of the metalnodes (clusters) and organic linkers, metal‐organic frameworks (MOFs) andtheir derivatives are rapidly gaining ground in the fabrication of electrocatalysts,with promising catalytic activity and sound durability in OER, thanksto their controllable pore structures, abundant unsaturated active sites of metalion, extensive specific surface area, as well as easily functionalized/modifiedsurfaces. This review presents an in‐depth understanding of the establishedprogress of MOFs‐derived materials for OER electrocatalysis. The materialdesigning strategies of the pristine, monometallic, and multimetallic MOFsbasedcatalysts are summarized to indicate the infinite possibilities of themorphology and the composition of MOF‐derived materials. While emphasisis laid on the essential features of MOF‐derived materials for the electrocatalysisof the corresponding reactions, insights about the applications in OERare discussed. Finally, this paper is concluded by presenting challengesand perspectives for MOF‐derived materials’ future applications in OERelectrocatalysis.

Iron-based binary metal-organic framework nanorods as an efficient catalyst for the oxygen evolution reaction

First-row transition metal compounds have been widely explored as oxygen evolution reaction(OER)electrocatalysts due to their impressive performance in this application.However,the activity trends of these electrocatalysts remain elusive due to the effect of inevitable iron impurities in alkaline electrolytes on the OER;the inhomogeneous structure of iron-based(oxy)hydroxides further complicates this situation.Bimetallic metal-organic frameworks(MOFs)have the advantages of well-defined and uniform atomic structures and the tunable coordination environments,allowing the structure-activity relationships of bimetallic sites to be precisely explored.Therefore,we prepared a series of iron-based bimetallic MOFs(denoted as Fe_(2)M-MIL-88B,M=Mn,Co,or Ni)and systematically compared their electrocatalytic performance in the OER in this work.All the bimetallic MOFs exhibited higher OER activity than their monometallic iron-based counterpart,with their activity following the order FeNi>FeCo>FeMn.In an alkaline electrolyte,Fe2Ni-MIL-88B showed the lowest overpotential to achieve a current density of 10 mA cm^(–2)(307 mV)and the smallest Tafel slope(38 mV dec^(–1)).The experimental and calculated results demonstrated that iron and nickel exhibited the strongest coupling effect in the series,leading to modification of the electronic structure,which is crucial for tuning the electrocatalytic activity.

Metal-Organic Frameworks Derived Ag-CoSO4 Nanohybrids as Efficient Electrocatalyst for Oxygen Evolution Reaction

Cobalt-based nanomaterials have been intensively explored as one of the most promising noble-metal-free oxygen evolution reaction (OER) electrocatalysts. However, most of their performances are still inferior to state-of-the-art precious metals especially for Ru and Ir.Herein, we apply a continuous ion exchange method and further hydrothermal treatment to synthesize the flake-like Ag-CoSO4 nanohybrids beginning from Co-BTC (BTC:benzene-1,3,5-tricarboxylic acid) metal-organic frameworks precursor. The catalyst exhibits superior OER performance under the alkaline electrolyte solution (a low overpotential of 282 mV at 10 mA/cm2 in 1 mol/L KOH), which is even better than RuO2 due to the improved conductivity and rapid electrons transfer process via introducing small amount of Ag. The existence of Ag in the hybrids is beneficial for increasing the Co(IV) concentration, thus promoting the *OOH intermediate formation process. Besides, due to the very low requirement of Ag content (lower than 1 atom%), the cost of the catalyst is also limited. This work provides a new insight for designing of inexpensive OER catalysts with high performance and low cost.

Cobalt/iron bimetal-organic frameworks as efficient electrocatalysts for the oxygen evolution reaction

The development of high efficiency and stable electrocatalysts for oxygen evolution is critical for energy storage and conversion systems. Herein, a series of Co/Fe bimetal-organic frameworks (MOFs) were fabricated using a facile ultrasonic method at room temperature, as electrocatalysts for the oxygen evolution reaction (OER) in alkaline solution. The Co2Fe-MOF exhibited an overpotential of 280 mV at a current density of 10 mA cm^-2, a low Tafel slope of 44.7 mV dec^-1, and long-term stability over 12000 s in 1 mol L^-1 KOH. This impressive performance was attributed to the high charge transfer rate, large specific surface area, and synergistic effects of the cobalt and iron centers.

Amorphous nickel-cobalt bimetal-organic framework nanosheets with crystalline motifs enable efficient oxygen evolution reaction: Ligands hybridization engineering

Development of high-efficiency and low-cost electrocatalyst for oxygen evolution reaction(OER) is very important for use at alkaline water electrolysis.Metal-organic frameworks(MOF) provide a rich platform for designing multi-functional materials due to their controllable composition and ultra-high surface area.Herein,we report our findings in the development of amorphous nickel-cobalt bimetal-organic framework nanosheets with crystalline motifs via a simple "ligands hybridization engineering" strategy.These complexes' ligands contain inorganic ligands(H_2 O and NO_3) and organic ones,hexamethylenetetramine(HMT).Further,we investigated a series of mixed-metal with multi-ligands materials as OER catalysts to explore their possible advantages and features.It is found that the Ni doping is an effective approach for optimizing the electronic configuration,changing lattice ordering degree,and thus enhancing activities of HMT-based electrocatalysts.Also,the crystalline-amorphous boundaries of various HMTbased electrocatalyst can be easily controlled by simply changing amounts of Ni-precursor added.As a result,the optimized ultrathin(Co,0.3 Ni)-HMT nanosheets can reach a current density of 10 mA cm^(-2)at low overpotential of 330 mV with a small Tafel slope of 66 mV dec^(-1).Our findings show that the electronic structure changes induced by Ni doping,2 D nanosheet structure,and MOF frameworks with multiligands compositions play critical roles in the enhancement of the kinetically sluggish electrocatalytic OER.The present study emphasizes the importance of ligands and active metals via hybridization for exploring novel efficient electrocatalysts.

2D/2D S-scheme heterojunction with a covalent organic framework and g-C_(3)N_(4) nanosheets for highly efficient photocatalytic H2 evolution

The fabrication of S-scheme heterojunctions with fast charge transfer and good interface contacts,such as intermolecularπ–πinteractions,is a promising approach to improve photocatalytic performance.A unique two-dimensional/two-dimensional(2D/2D)S-scheme heterojunction containing TpPa-1-COF/g-C_(3)N_(4) nanosheets(denoted as TPCNNS)was developed.The established maximum interfacial interaction between TpPa-1-COF NS and g-C_(3)N_(4) NS may result in aπ–πconjugated heterointerface.Furthermore,the difference in the work functions of TpPa-1-COF and g-C_(3)N_(4) results in a large Fermi level gap,leading to upward/downward band edge bending.The spontaneous interfacial charge transfer from g-C_(3)N_(4) to TpPa-1-COF at theπ–πconjugated interface area results in the presence of a built-in electric field,according to the charge density difference analysis based on density functional theory calculations.Such an enhanced built-in electric field can efficiently drive directional charge migration via the S-scheme mechanism,which enhances charge separation and utilization.Thus,an approximately 2.8 and 5.6 times increase in the photocatalytic hydrogen evolution rate was recorded in TPCNNS-2(1153μmol g^(-1) h^(-1))compared to pristine TpPa-1-COF and g-C_(3)N_(4) NS,respectively,under visible light irradiation.Overall,this work opens new avenues in the fabrication of 2D/2Dπ–πconjugated S-scheme heterojunction photocatalysts with highly efficient hydrogen evolution performance.

Evolution of corporate environmental information disclosure framework of “knowledge and action”: Based on big data background

Cloud accounting is based on the traditional financial work process, the context of big data, and the necessary trend of future corporate accounting development. Its emergence and rapid development will have a fundamental impact on corporate environmental information disclosure. In the big data era of information sharing, companies will have a new understanding of the emergence, balance, and final consideration of social responsibility, and will have new changes in their overall decision-making and information disclosure methods. "Knowing" and "behavior" will be combined on the basis of rational judgment, so that corporate environmental information disclosure is more in line with the overall social development requirements. Based on the background of big data, this article starts with the disclosure of impact factors, footholds, and path choices. It describes the evolution of corporate environmental information disclosure and provides reference suggestions for enterprises to disclose environmental information truthfully and perform social responsibilities.

A 2D NiFe Bimetallic Metal–Organic Frameworks for Efficient Oxygen Evolution Electrocatalysis

The oxygen evolution reaction(OER) is the cornerstone for many important energy conversion devices, including metal–air battery and water splitting.Herein, an optimized NiFe-based metal–organic framework is developed as highly efficient active material for OER. It just needs a low overpotential of 0.31 V to deliver a current density of 10 mA cm-2 with a favorable Tafel slope of 43.7 mV dec-1 in 0.1 M KOH electrolyte for the as-prepared Ni0.75Fe0.25 BDC, which is superior to RuO2. This efficient catalytic performance is due to the introduction of Fe in Ni-based MOFs could benefit the kinetics and charge transfer efficiency, resulting in the optimal activity toward OER. Besides, the obtained active material demonstrates good stability, suggesting the great potential value in sustainable electrochemical energy storage and conversion devices.

A framework for Internet service evolution based on active object

The wide use of Internet Service in distributed computing and e-business has made the evolution of Internet Service to be one of the most prevalent research fields in software development domain. Traditional methods for software development cannot adapt to the challenge of Internet Service oriented software development. In this paper, we propose a new paradigm for the evolution of Internet Service with active objects from the characteristics of Intemet Service and principles of active objects. The paradigm uses an automatic monitoring mechanism of active object to detect and process evolution requirement in system based on Internet Service.

A new strategy for the fabrication of covalent organic framework‐metal‐organic framework hybrids via in‐situ functionalization of ligands for improved hydrogen evolution reaction activity

The development of novel porous materials have attracted significant attention owing to its possible application in several fields.In this study,we designed a novel covalent organic framework‐metal‐organic framework(COF‐MOF)material through an in‐situ ligand self‐assembly method.The in‐situ modified ligands not only act as nucleation sites to form Ti‐MOF,but also as a channel to rapidly transfer photogenerated electrons without introducing additional chemical bonds.The photocatalytic hydrogen production rate achieved over B‐CTF‐Ti‐MOF(1:1)was 1975μmol·g^(–1)·h^(–1) with an apparent quantum efficiency of 4.76%,which is 11.8 times higher than that of the pure CTF‐1.In addition,compared with the sample prepared by separating the ligands(CTF‐1/Ti‐MOF),B‐CTF‐Ti‐MOF shows excellent activity and stability.Finally,a reasonable photocatalytic mechanism was proposed using the results of electrochemical tests and spectral analyses.This study provides a universal method for the construction of highly efficient and stable COF/MOF materials with excellent properties.

Carambola-like metal-organic frameworks for high-performance electrocatalytic oxygen evolution reaction

Hydrogen production by electrocatalytic water splitting promises a green and sustainable technology to address serious energy crisis and environmental pollution [1]. As well known, the process of electrocatalytic water splitting is composed of two half reaction, i.e. oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode [2].

Metal-organic framework derived NiFe_(2)O_(4)/FeNi_(3)@C composite for efficient electrocatalytic oxygen evolution reaction

Reducing the cost and improving the electrocatalytic activity are the key to developing high efficiency electrocatalysts for oxygen evolution reaction(OER).Here,bimetallic NiFe-based metal-organic framework(MOF)was prepared by solvothermal method,and then used as precursor to prepare NiFe-based MOF-derived materials by pyrolysis.The effects of different metal ratios and pyrolysis temperatures on the sample structure and OER electrocatalytic performance were investigated and compared.The experimental results showed that when the metal molar ratio was Fe:Ni=1:5 and the pyrolysis temperature was 450℃,the sample(FeNi_(5)-MOF-450)exhibits a composite structure of Ni Fe_(2)O_(4)/FeNi_(3)/C and owns the superior electrocatalytic activity in OER.When the current density is 100 mA·cm^(-2),the overpotential of the sample was 377 mV with Tafel slope of 56.2 mV·dec^(-1),which indicates that FeNi_(5)-MOF-450 exhibits superior electrocatalytic performance than the commercial RuO_(2).Moreover,the long-term stability of FeNi_(5)-MOF-450 further promotes its development in OER.This work demonstrated that the regulatory methods such as component optimization can effectively improve the OER catalytic performance of NiFe-based MOF-derived materials.

Message Service System Evolution and General Frameworks

With the development of message service in telecom networks as well as the Internet,multiple message service formats have been emerging,including Short Message Service (SMS),Multimedia Messaging Service (MMS),Mobile Email Message (MEM) and Instant Message (IM).Based on the latest research achievements of OMA CPM Organization and GSMA RCS Organization,the message service evolution may have two phases:Integration and convergence,with corresponding overall framework realization methods.

Framework for a System of Systems Design Oriented to Evolution

A framework was proposed for designing a system of systems(SoS) that takes account of the system' s evolution over time.Given the design space of the SoS analysis,construct a multiepoch scenario design,SoS optimization,and robust designs.A hybrid model based on multi-agent and system dynamic models was used to analyze the evolution of an SoS and find robust designs.The framework can help decision makers generate a robust SoS structure based on the SoS' s capabilities over multiple epochs.