Single-atom catalysts based on polarization switching of ferroelectric In_(2)Se_(3) for N_(2) reduction

The polarization switching plays a crucial role in controlling the final products in the catalytic pro-cess.The effect of polarization orientation on nitrogen reduction was investigated by anchoring transition metal atoms to form active centers on ferroelectric material In_(2)Se_(3).During the polariza-tion switching process,the difference in surface electrostatic potential leads to a redistribution of electronic states.This affects the interaction strength between the adsorbed small molecules and the catalyst substrate,thereby altering the reaction barrier.In addition,the surface states must be considered to prevent the adsorption of other small molecules(such as *O,*OH,and *H).Further-more,the V@↓-In_(2)Se_(3) possesses excellent catalytic properties,high electrochemical and thermody-namic stability,which facilitates the catalytic process.Machine learning also helps us further ex-plore the underlying mechanisms.The systematic investigation provides novel insights into the design and application of two-dimensional switchable ferroelectric catalysts for various chemical processes.

Non-isothermal reduction kinetics of Fe_2O_3-NiO composites for formation of Fe-Ni alloy using carbon monoxide

The non-isothermal reduction kinetics and mechanism of Fe2O3-NiO composites with different Fe2O3-NiO compacts using carbon monoxide as reductant were investigated. The results show that the reduction degree increases rapidly with increasing the content of NiO, and the presence of NiO also improves the reduction rate of iron oxides. It is found that NiO is preferentially reduced at the beginning of the reactions, and then the metallic Ni acts as a catalyst promoting the reduction rate of iron oxides. It is also observed that the increase of the Ni O content enhances the formation of awaruite(FeNi3) but decreases the percentage of kamacite(Fe,Ni) and taenite(Fe,Ni). The particle size of the materials tends to be uniform during the reduction process due to the presence of metallic nickel, metallic iron and the formation of Fe-Ni alloy. The concentration of CO in the product gas is greater than that of CO2 at the beginning of the reaction and then slows down. The fastest reduction rate of Fe2O3-NiO composites with CO appears at 400-500 °C, and nucleation growth model can be used to elucidate the reduction mechanism. Nucleation growth process is found to be the rate controlling step when the temperature is lower than 1000 °C.

Fe-Beta zeolite for selective catalytic reduction of NO_x with NH_3:Influence of Fe content

Fe doped Beta zeolite with different Fe contents were prepared by ion exchange by changing the volume or the concentration of a Fe salt solution. For a particular mass of Fe salt precursor, the concentration of the metal salt solution during ion exchange influenced the ion exchange capacity of Fe, and resulted in different activities of the Fe-Beta catalyst. Fe-Beta catalysts with the Fe contents of （2.6, 6.3 and 9） wt% were synthesized using different amounts of 0.02 mol/L Fe salt solution. These catalysts were studied by various characterization techniques and their NH3-SCR activities were evaluated. The Fe-Beta catalyst with the Fe content of 6.3 wt% exhibited the highest activity, with a temperature range of 202-616℃ where the NOx conversion was 〉 80%. The Fe content in Beta zeolite did not influence the structure of Beta zeolite and valence state of Fe. Compared with the Fe-Beta catalysts with low Fe content （2.6 wt%）, Fe-Beta catalysts with 6.3 wt% Fe content possessed more isolated Fe3. active sites which led to its higher NH3-SCR activity. A high capacity for NH3 and NO adsorption, and a high activity for NO oxidation also contributed to the high NH3-SCR activity of the Fe-Beta catalyst with 6.3 wt%. However, when the Fe content was further increased to 9.0 wt%, the amount of FexOy nanoparticles increased while the amount of isolated Fe3＋ active sites was unchanged, which promoted NH3 oxidation and decreased the NH3-SCR activity at high temperature.

Highly selective photocatalytic reduction of CO_(2) to CH_(4) on electron-rich Fe species cocatalyst under visible light irradiation

Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great challenges.Herein,we demonstrate unprecedented hybrid SiC photocatalysts modified by Fe-based cocatalyst,which are prepared via a facile impregnation-reduction method,featuring an optimized local electronic structure.It exhibits a superior photocatalytic carbon-based products yield of 30.0μmol g^(−1) h^(−1) and achieves a record CH_(4) selectivity of up to 94.3%,which highlights the effectiveness of electron-rich Fe cocatalyst for boosting photocatalytic performance and selectivity.Specifically,the synergistic effects of directional migration of photogenerated electrons and strongπ-back bonding on low-valence Fe effectively strengthen the adsorption and activation of reactants and intermediates in the CO_(2)→CH_(4) pathway.This study inspires an effective strategy for enhancing the multielectron reduction capacity of semiconductor photocatalysts with low-cost Fe instead of noble metals as cocatalysts.

Pre-reduction of WO_(3)-Co_(3)O_(4)by H_(2)-C_(2)H_4 in a fluidized bed

In order to avoid the formation ofηphase(W_(6)Co_(6)C or W_(3)Co_(3)C)that adversely affects the sintering process and its products in the preparation process of ultra-fine WC-Co powder,a technical route of prereduction of WO_(3)-Co_(3)O_(4)to WO_(2)-Co and then deep reduction carbonization to WC-Co powder has been proposed.This study mainly investigates the influence of gas partial pressure on the pre-reduction process of WO_(3)-Co_(3)O_(4)under a mixed atmosphere of H_(2)-C_(2)H_(4)-Ar at 600℃and establishes the kinetic equations of pre-reduction and carbon evolution.The results indicate that increasing the partial pressure of hydrogen is conducive to the rapid and complete conversion of WO_(3) to WO_(2).High carbon content can be generated by the deposition of C_(2)H_(4),and it hinders the diffusion of the reducing gas;WO_(3)still cannot be completely reduced to WO_(2)as the partial pressure of C_(2)H_(4) increases to 60%.For the carbon evolution of C_(2)H_(4),the carbon amount is positively related to the H_(2)partial pressure,but it shows the highest amount and evolution rate when the ethylene partial pressure is 20%.Based on the reduction rate curves of WO_(3) and carbon evolution rate curves of C_(2)H_(4),the rate equations of pre-reduction and carbon evolution of WO_(3)-Co_(3)O_(4)system at 600℃are established.The pre-reduction reaction belongs to the first-order reaction,and its equation is expressed as follows:r=-(dw_(WO_(3)))/dt=(9±0.15)×10^(-2)×P_(H_(2))^(0.44)P_(C_(2)H_(4))&(0.57)The carbon deposition rate equation of C_(2)H_(4) can be expressed as follows:r=-(dc_C)/dt=r_f-r_b≌7.35×10^(-2)×P_(C_(2)H_(4))^(0.31)

Atomically dispersed Fe sites on hierarchically porous carbon nanoplates for oxygen reduction reaction

Developing cost-effective,robust and stable non-precious metal catalysts for oxygen reduction reaction(ORR) is of paramount importance for electrochemical energy conversion devices such as fuel cells and metal-air batteries.Although Fe-N-C single atom catalysts(SACs) have been hailed as the most promising candidate due to the optimal binding strength of ORR intermediates on the Fe-N_(4) sites,they suffer from serious mass transport limitations as microporous templates/substrates,i.e.,zeolitic imidazolate frameworks(ZIFs),are usually employed to host the active sites.Motivated by this challenge,we herein develop a hydrogen-bonded organic framework(HOF)-assisted pyrolysis strategy to construct hierarchical micro/mesoporous carbon nanoplates for the deposition of atomically dispersed Fe-N_(4) sites.Such a design is accomplished by employing HOF nanoplates assembled from 2-aminoterephthalic acid(NH_(2)-BDC) and p-phenylenediamine(PDA) as both soft templates and C,N precursors.Benefitting from the structural merits inherited from HOF templates,the optimized catalyst(denoted as Fe-N-C SAC-950) displays outstanding ORR activity with a high half-wave potential of 0.895 V(vs.reversible hydrogen electrode(RHE)) and a small overpotential of 356 mV at 10 mA cm^(-2) for the oxygen evolution reaction(OER).More excitingly,its application potential is further verified by delivering superb rechargeability and cycling stability with a nearly unfading charge-discharge gap of 0.72 V after 160 h.Molecular dynamics(MD) simulations reveal that micro/mesoporous structure is conducive to the rapid mass transfer of O_(2),thus enhancing the ORR performance.In situ Raman results further indicate that the conversion of O_(2) to~*O_(2)-the rate-determining step(RDS) for Fe-N-C SAC-950.This work will provide a versatile strategy to construct single atom catalysts with desirable catalytic properties.

Preparation of low-oxygen titanium powder by magnesiothermic reduction of TiO2 assisted by MgCl_(2)−HoCl_(3) molten salt

To reduce the production cost of titanium,a new method for direct preparation of low-oxygen titanium powder by the magnesiothermic reduction of TiO_(2) with the assistance of a MgCl_(2)−HoCl_(3) molten salt was proposed.Thermodynamic calculations showed that the magnesiothermic reduction of TiO_(2) was feasible.However,hindrance of the reduction reaction by the reduction by-product of MgO resulted in a considerably high O concentration in the titanium powder.The addition of HoCl_(3) to the system significantly reduces the activity of MgO to produce low-oxygen titanium powder.Thermochemical deoxidation and reduction experiments were conducted with MgCl_(2)−HoCl_(3) molten salt in the temperature range of 1023−1273 K.The results showed that titanium powder with oxygen concentration(mass fraction)below 5.00×10^(-4) can be prepared at the Mg−MgCl_(2)−HoOCl−HoCl_(3) equilibrium.

FCF-LDH/BiVO_(4)with synergistic effect of physical enrichment and chemical adsorption for efficient reduction of nitrate

Photoelectrochemical NO_(3)^(-)reduction(PEC NITRR)not only provides a promising solution for promoting the global nitrogen cycle,but also converts NO_(3)^(-)to the important chemicals(NH_(3)).However,it is still a great challenge to prepare catalysts with excellent NO_(3)^(-)adsorption/activation capacity to achieve high NITRR.Herein,we designed a novel Fe^(2+)~Cu^(2+)Fe^(3+)LDH/BiVO_(4)(FCF-LDH/BVO)catalyst with synergistic effect of chemical adsorption and physical enrichment.Fe^(2+)in FCF-LDH/BVO provides the rich Lewis acid sites for the adsorption of NO_(3)^(-),and the appropriate layer spacing of FCF-LDH further promotes the physical enrichment of NO_(3)^(-)in its interior,thus realizing the effective contact between NO_(3)^(-)and active sites(Fe^(2+)).FCF-LDH/BVO showed excellent NH_(3)production performance(FE_(NH_(3))=66.1%,r_(NH_(3))=13.8μg h^(-1)cm^(-2))and selectivity(FE_(NO_(2)^(-))=2.5%,r_(NO_(2)^(-))=4.9μg h^(-1)cm^(-2))in 0.5 mol L^(-1)Na_(2)SO_(4)electrolyte.In addition,FCF-LDH/BVO maintains the desirable PEC stability for six cycle experiments,showing great potential for practical application.The^(14)NO_(3)^(-)and^(15)NO_(3)^(-)isotope test provides strong evidence for further verification of the origin of N in the generated NH_(3).This LDH catalyst has a great potential in PEC removal of NO_(3)^(-)from groundwater.

Catalytic Performance of Aquathermolysis and Viscosity Reduction of Heavy Oil over a WO_(3)/ZrO_(2) Solid Acid

Tungstated zirconia(WO_(3)/ZrO_(2))solid acid catalysts with different WO_(3) contents were prepared by a hydrothermal method and then used in the catalytic aquathermolysis of heavy oil from Xinjiang.The WO_(3)/ZrO_(2) solid acid catalyst was characterized by a range of characterization methods,including X-ray diffraction,NH3-temperature programmed desorption,and pyridine infrared spectroscopy.The WO_(3) content of the WO_(3)/ZrO_(2) catalysts had an important impact on the structure and property of the catalysts.When the WO_(3) mass fraction was 20%,it facilitated the formation of tetragonal zirconia,thereby enhancing the creation of robust acidic sites.Acidity is considered to have a strong impact on the catalytic performance of the aquathermolysis of heavy oil.When the catalyst containing 20%WO_(3) was used to catalyze the aquathermolysis of heavy oil under conditions of 14.5 MPa,340℃,and 24 h,the viscosity of heavy oil decreased from 47266 to 5398 mPa·s and the viscosity reduction rate reached 88.6%.The physicochemical properties of heavy oil before and after the aquathermolysis were analyzed using a saturates,aromatics,resins,and asphaltenes analysis,gas chromatography,elemental analysis,densimeter etc.After the aquathermolysis,the saturate and aromatic contents significantly increased from 43.3%to 48.35%and 19.47%to 21.88%,respectively,with large reductions in the content of resin and asphaltene from 28.22%to 25.06%and 5.36%to 2.03%,respectively.The sulfur and nitrogen contents,and the density of the oil were significantly decreased.These factors were likely the main reasons for promoting the viscosity reduction of heavy oil during the aquathermolysis over the WO_(3)/ZrO_(2) solid acid catalysts.

Engineering asymmetric electronic structure of cobalt coordination on CoN_(3)S active sites for high performance oxygen reduction reaction

The efficacy of the oxygen reduction reaction(ORR) in fuel cells can be significantly enhanced by optimizing cobalt-based catalysts,which provide a more stable alternative to iron-based catalysts.However,their performance is often impeded by weak adsorption of oxygen species,leading to a 2e^(-)pathway that negatively affects fuel cell discharge efficiency.Here,we engineered a high-density cobalt active center catalyst,coordinated with nitrogen and sulfur atoms on a porous carbon substrate.Both experimental and theoretical analyses highlighted the role of sulfur atoms as electron donors,disrupting the charge symmetry of the original Co active center and promoting enhanced interaction with Co 3d orbitals.This modification improves the adsorption of oxygen and reaction intermediates during ORR,significantly reducing the production of hydrogen peroxide(H_(2)O_(2)).Remarkably,the optimized catalyst demonstrated superior fuel cell performance,with peak power densities of 1.32 W cm^(-2) in oxygen and 0.61 W cm^(-2) in air environments,respectively.A significant decrease in H_(2)O_(2) by-product accumulation was observed during the reaction process,reducing catalyst and membrane damage and consequently improving fuel cell durability.This study emphasizes the critical role of coordination symmetry in Co/N/C catalysts and proposes an effective strategy to enhance fuel cell performance.

Mesoporous Carbon Nanofibers Loaded with Ordered PtFe Alloy Nanoparticles for Electrocatalytic Nitrate Reduction to Ammonia

Highly dispersed bimetallic alloy nanoparticle electrocatalysts have been demonstrated to exhibit exceptional performance in driving the nitrate reduction reaction(NO_(3)RR)to generate ammonia(NH_(3)).In this study,we prepared mesoporous carbon nanofibers(mCNFs)functionalized with ordered PtFe alloys(O-PtFe-mCNFs)by a composite micelle interface-induced co-assembly method using poly(ethylene oxide)-block-polystyrene(PEO-b-PS)as a template.When employed as electrocatalysts,O-PtFe-mCNFs exhibited superior electrocatalytic performance for the NO_(3RR)compared to the mCNFs functionalized with disordered PtFe alloys(D-PtFe-mCNFs).Notably,the NH_(3)production performance was particularly outstanding,with a maximum NH_(3)yield of up to 959.6μmol/(h·cm~2).Furthermore,the Faraday efficiency(FE)was even 88.0%at-0.4 V vs.reversible hydrogen electrode(RHE).This finding provides compelling evidence of the potential of ordered PtFe alloy catalysts for the electrocatalytic NO_(3)RR.

Comparison of reduction behavior of Fe_2O_3, ZnO and ZnFe_2O_4 by TPR technique

Advanced integrated gasification combined cycle （IGCC） power generation systems require the development of high-temperature, regenerable, desulfurization sorbents capable of removing hydrogen sulfide from coal gasifier gas to very low levels. As a sort of effective desufurizer, such as Fe2O3, ZnO and ZnFe2O4, it will endure strong reducing atmosphere in desulfurization process. The reduced degree of desufurizer can have an effect on its desulfurization reactivity. In this paper, Fe2O3, ZnO and ZnFe2O4 were synthesized by precipitation or co-precipitation at constant pH. After aging, washing and drying, the solids were calcined at 800℃. The reduction behaviors of sample were characterized by temperature-programmed reduction （TPR）. It is found that there are two reduction peaks for Fe2O3 in TPR, and whereas no reduction peaks for ZnO are found. The reduction process of ZnFe2O4 prepared by co-precipitation is different from that of Fe2O3. ZnFe2O4 is easier to be reduced than Fe2O3. The activation energy of reduction process for Fe2O3 and ZnFe2O4 is obtained at different reduction periods.

Enhanced photocatalytic Cr(Ⅵ) reduction and diclofenac sodium degradation under simulated sunlight irradiation over MIL-100(Fe)/g-C_3N_4 heterojunctions

Metal‐organic framework MIL‐100(Fe)and g‐C3N4 heterojunctions(MG‐x,x=5%,10%,20%,and 30%,x is the mass fraction of MIL‐100(Fe)in the hybrids)were facilely fabricated through ball‐milling and annealing,and characterized by powder X‐ray diffraction,Fourier transform infrared spectroscopy,thermogravimetric analysis,transmission electron microscopy,UV‐visible diffuse‐reflectance spectrometry,and photoluminescence emission spectrometry.The photocatalytic activities of the series of MG‐x heterojunctions toward Cr(VI)reduction and diclofenac sodium degradation were tested upon irradiation with simulated sunlight.The influence of different organic compounds(ethanol,citric acid,oxalic acid,and diclofenac sodium)as hole scavengers and the pH values(2,3,4,6,and 8)on the photocatalytic activities of the series of MG‐x heterojunctions was investigated.MG‐20%showed superior photocatalytic Cr(VI)reduction and diclofenac sodium degradation performance than did the individual MIL‐100(Fe)and g‐C3N4 because of the improved separation of photoinduced electron‐hole charges,which was clarified via photoluminescence emission and electrochemical data.Moreover,the MG‐x exhibited good reusability and stability after several runs.

Low-Temperature Selective Catalytic Reduction of NO with NH_3 over Fe–Ce–O_x Catalysts

In this study, we used a simple impregnation method to prepare Fe-Ce-O x catalysts and tested them regarding their low-temperature (200-300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94-99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h−1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80-98% between 200 and 300 °C at a space velocity of 204,000 h−1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200-300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance.

Inducing Fe 3d Electron Delocalization and Spin‑State Transition of FeN_(4) Species Boosts Oxygen Reduction Reaction for Wearable Zinc–Air Battery

Transition metal-nitrogen-carbon materials(M-N-Cs),particularly Fe-N-Cs,have been found to be electroactive for accelerating oxygen reduction reaction(ORR)kinetics.Although substantial efforts have been devoted to design Fe-N-Cs with increased active species content,surface area,and electronic conductivity,their performance is still far from satisfactory.Hitherto,there is limited research about regulation on the electronic spin states of Fe centers for Fe-N-Cs electrocatalysts to improve their catalytic performance.Here,we introduce Ti_(3)C_(2) MXene with sulfur terminals to regulate the electronic configuration of FeN_(4) species and dramatically enhance catalytic activity toward ORR.The MXene with sulfur terminals induce the spin-state transition of FeN_(4) species and Fe 3d electron delocalization with d band center upshift,enabling the Fe(II)ions to bind oxygen in the end-on adsorption mode favorable to initiate the reduction of oxygen and boosting oxygen-containing groups adsorption on FeN_(4) species and ORR kinetics.The resulting FeN_(4)-Ti_(3)C_(2)Sx exhibits comparable catalytic performance to those of commercial Pt-C.The developed wearable ZABs using FeN_(4)-Ti_(3)C_(2)Sx also exhibit fast kinetics and excellent stability.This study confirms that regulation of the electronic structure of active species via coupling with their support can be a major contributor to enhance their catalytic activity.

High efficient oxygen reduction performance of Fe/Fe3C nanoparticles in situ encapsulated in nitrogen-doped carbon via a novel microwave-assisted carbon bath method

Fe-based carbon materials are widely considered promising to replace Pt/C as next-generation electrocatalysts towards oxygen reduction reaction (ORR). However, the preparation of Fe-based carbon materials is still carried out by conventional heating method (CHM). Herein, a novel microwave-assisted carbon bath method (MW-CBM) was proposed, which only took 35 min to synthesize Fe/Fe3C nanoparticles encapsulated in N-doped carbon layers derived from Prussian blue (PB). The catalyst contained large specific surface area and mesoporous structure, abundant Fe-Nx and C–N active sites, unique core-shell structure. Due to the synergistic effects of these features, the as-prepared Fe/Fe3C@NC-2 displayed outstanding ORR activity with onset potential of 0.98 VRHE and halfwave potential of 0.87 VRHE, which were more positive than 20 wt.% Pt/C (0.93 VRHE and 0.82 VRHE). Besides, Fe/Fe3C@NC-2 gave a better stability and methanol tolerance than Pt/C towards ORR in alkaline media, too.

Effect of CaO and CaCO3 on Reduction Rate of Iron Ore Pellets Containing Carbon

The effect of metallurgical fluxes CaO and CaCO3 on the reduction rate of iron ore pellets containing carbon in nitrogen atmosphere has been studied by a weight-loss thermal balance. The experimental results showed that adding CaO or CaCO3 can promote reduction reaction as the added CaO or CaCO3 probably decrease the apparent activation energy of iron ore concentrate-carbon-CaO or CaCO3 reaction, and the reduction rate constant changes with mass percent of CaO and CaCO3. The kinetic analysis also showed that the rate-controlling step of the reaction is inner gas diffusion.

In situ preparation of mesoporous Fe/TiO_2 catalyst using Pluronic F127-assisted sol-gel process for mid-temperature NH_3 selective catalytic reduction

An Fe/TiO2catalyst with uniform mesopores was synthesized using Pluronic F127as a structuredirecting agent.This catalyst was used for selective catalytic reduction of NO with NH3.The catalytic activity and resistance to H2O and SO2of Fe/TiO2prepared by a template method were better than those of catalysts synthesized using impregnation and coprecipitation.The samples were characterized using N2‐physisorption,transmission electron microscopy,ultraviolet‐visibl spectroscopy,X‐ray photoelectron spectroscopy,and in situ diffuse reflectance infrared Fouriertransform spectroscopy.The results showed that Pluronic F127acted as a structural and chemical promoter;it not only promoted the formation of a uniform mesoporous structure,leading to a higher surface area,but also improved dispersion of the active phase.In addition,the larger number of Lewis acidic sites,indicated by the presence of coordinated NH3species(1188cm-1)and the N–H stretching modes of coordinated NH3(3242and3388cm-1),were beneficial to mid‐temperature selective catalytic reduction reactions.

Effect of B2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of the chromium-bearing vanadium titanomagnetite pellets (CVTP) with B2O3 addition were investigated. Besides, the reduction swelling index (RSI) and compressive strength (CS) of the reduced CVTP were also examined using the simulated coke oven gas (COG). The results suggested that the CS of CVTP was increased from 2448 to 3819.2 N, while the porosity of CVTP was decreased from 14.86% to 10.03% with the increase in B2O3 addition amounts. Moreover, the B2O3 mainly existed in the forms of TiB0.024O2 and Fe3BO5 in both CVTP and the reduced CVTP. Specifically, the CS of the reduced CVTP was elevated from 901 to 956.2 N, while the RSI was reduced from 5.87% to 3.81% as the B2O3 addition amounts were increased. Taken together, B2O3 addition would facilitate the aggregation and diffusion of metallic iron particles, which contributed to reducing the formation of metal iron whiskers and weakening the reduction swelling behavior.

3D Fe-MOF embedded into 2D thin layer carbon nitride to construct 3D/2D S-scheme heterojunction for enhanced photoreduction of CO_(2)

Regulating charge transfer to achieve specific transfer path can improve electron utilization and complete efficient photoreduction of CO_(2).Here,we fabricated a S-scheme heterojunction of CN/Fe-MOF by an in-situ assembly strategy.The S-scheme charge transfer mechanism was confirmed by band structure,electron spin resonance(ESR)and work function(Φ)analysis.On the one hand,the response of Fe-MOF in the visible region improved the utilization of light energy,thus increasing the ability of CN/Fe-MOF to generate charge carriers.On the other hand,CN,as the active site,not only had strong adsorption capacity for CO_(2),but also retained photogenerated electrons with high reduction capacity because of S-scheme charge transfer mechanism.Hence,in the absence of any sacrificial agent and cocatalyst,the optimized 50CN/Fe-MOF obtained the highest CO yield(19.17μmol g^(–1))under UV-Vis irradiation,which was almost 10 times higher than that of CN.In situ Fourier transform infrared spectra not only revealed that the photoreduction of CO_(2) occurred at the CN,but also demonstrated that the S-scheme charge transfer mechanism enabled 50CN/Fe-MOF to have a stronger ability to generate HCOO–than CN.