Adsorptive removal of nitrogen-containing compounds from fuel by metal-organic frameworks

The adsorptive denitrogenation from fuels over three metal-organic frameworks(MIL-96(Al),MIL-53(Al)and MIL-101(Cr))was studied by batch adsorption experiments.Four nitrogen-containing compounds(NCCs)pyridine,pyrrole,quinoline and indole were used as model NCCs in fuels to study the adsorption mechanism.The physicochemical properties of the adsorbents were characterized by XRD,N2physical adsorption,FT-IR spectrum and Hammett indicator method.The metal-organic frameworks(MOFs),especially the MIL-101(Cr)containing Lewis acid sites as well as high specific surface area,can adsorb large quantities of NCCs from fuels.In addition,the adsorptive capacity over MIL-101(Cr)will be different for NCCs with different basicity.The stronger basicity of the NCC is,the more it can be absorbed over MIL-101(Cr).Furthermore,pore size and shape also affect the adsorption capacity for a given adsorbate,which can be proved by the adsorption over MIL-53(Al)and MIL-96(Al).The pseudo-second-order kinetic model and Langmuir equation can be used to describe kinetics and thermodynamics of the adsorption process,respectively.Finally,the regeneration of the used adsorbent has been conducted successfully by just washing it with ethanol.

Water-based synthesis of nanoscale hierarchical metal-organic frameworks:Boosting adsorption and catalytic performance

The combination of nano sizes,large pore sizes and green synthesis is recognized as one of the most crucial and challenging problems in constructing metal-organic frameworks(MOFs).Herein,a water-based strategy is proposed for the synthesis of nanoscale hierarchical MOFs(NH-MOFs)with high crystallinity and excellent stability.This approach allows the morphology and porosity of MOFs to be fine tuned,thereby enabling the nanoscale crystal generation and a well-defined hierarchical system.The aqueous solution facilitates rapid nucleation kinetics,and the introduced modulator acts as a deprotonation agent to accelerate the deprotonation of the organic ligand as well as a structure-directing agent(SDA)to guide the formation of hierarchical networks.The assynthesized NH-MOFs(NH-ZIF-67)were assessed as efficient adsorbents and heterogeneous catalysts to facilitate the diffusion of guest molecules,outperforming the parent microZIF-67.This study focuses on understanding the NH-MOF growth rules,which could allow tailor-designing NH-MOFs for various functions.

Research progress on metal-organic framework compounds(MOFs)in electrocatalysis

Metal-organic frameworks(MOFs)have favorable characteristics such as large specific surface area,high porosity,structural diversity,and pore surface modification,giving them great potential for development and attractive prospects in the research area of modern materials electrocatalysis.However,unsatisfactory catalytic activity and poor electronic conductivity are the main challenges facing MOFs.This review focuses on MOF-based materials used in electrocatalysis,based on the types of catalytic reactions that have used MOF-based materials in recent years along with their applications,and also looks at some new electrocatalytic materials and their future development prospects.

Interfacial features of TiAl alloy/316L stainless steel joint brazed with Zr−Cu−Ni−Al amorphous filler metal

TiAl alloy and 316L stainless steel were vacuum-brazed with Zr−50.0Cu−7.1Ni−7.1Al(at.%)amorphous filler metal.The influence of brazing time and temperature on the interfacial microstructure and shear strength of the resultant joints was investigated.The brazed seam consisted of three layers,including two diffusion layers and one residual filler metal layer.The typical microstructure of brazed TiAl alloy/316L stainless steel joint was TiAl alloy substrate/α2-(Ti3Al)/AlCuTi/residual filler metal/Cu9Zr11+Fe23Zr6/Laves-Fe2Zr/α-(Fe,Cr)/316L stainless steel substrate.Discontinuous brittle Fe2Zr layer formed near the interface between the residual filler metal layer andα-(Fe,Cr)layer.The maximum shear strength of brazed joints reached 129 MPa when brazed at 1020℃ for 10 min.The diffusion activation energies ofα2-(Ti3Al)andα-(Fe,Cr)phases were−195.769 and−112.420 kJ/mol,respectively,the diffusion constants for these two phases were 3.639×10^(−6) and 7.502×10^(−10)μm^(2)/s,respectively.Cracks initiated at Fe2Zr layer and propagated into the residual filler metal layer during the shear test.The Laves-Fe2Zr phase existing on the fracture surface suggested the brittle fracture mode of the brazed joints.

Roadmap of amorphous metal-organic framework for electrochemical energy conversion and storage

Metal-organic frameworks(MOFs),a well-known coordination network involving potential voids,have attracted attention for energy conversion and storage.As far as is known,MOFs are not only believed to be crystalline.Emerging amorphous MOFs(aMOFs)are starting as supplementary to crystalline MOF(cMOF)in various electrochemical energy fields owing to intrinsic superiorities over crystalline states,greater ease of processing,and distinct physical and chemical properties.aMOFs retain the basic skeletons and connectivity of building units but without any long-range order.Such structural features over long range possess the isotropy without grain boundaries,resulting in fast ions flux and uniform distribution.Simultaneously,distinct shortrange characteristics provide diverse pore confined environment and abundant active sites,and thus accelerate mass transport and charge transfer during electrochemical reactions.Deep understandings and controllable design of aMOF may broaden the opportunities for both scientific researches beyond crystalline materials and practical applications.To date,comprehensive reviews about aMOFs in the fields of energy conversion and storage remain woefully underrepresented.Herein,we summarize the roadmap of aMOF from the development,structural design,opportunity,application,bottleneck,and perspective.In-depth structure-activity relationships with aMOF chemistry are highlighted in the typical electrochemical energy conversion like water oxidation and energy storage,including supercapacitor and battery.The combination of disordered nature at long range and short range,alongside the dynamic structural changes,is promising to reinforce cognition of aMOF domains with MOF versatility,shedding light on the design for efficient electrochemical energy applications via amorphization.

Preliminary analysis on roles of metal–organic compounds in the formation of invisible gold

The paper comprises new analytical data on the nature and occurrence of gold in solid pyrobitumen,closely associated with the main gold-bearing sulfide arsenic ores of the Bakyrchik gold deposit(Kazakhstan),related to post-collisional magmatic-hydrothermal origin.Gold mineralization of the deposit occurs mainly in the form of an“invisible”type of gold in the structures of arsenian pyrite and arsenopyrite,and the form of gold-organic compounds of pyrobitumen in carbonaceous-terrigenous sequences of Carboniferous formation.Microscopic and electron microscopic analysis,Raman and FT-Infrared analysis,mineralogical and three-step sequential extraction analysis(NH2OHHCl,H2O2,HNO3?HCl)has been carried out using 9 ore samples(from 3 different types of ores)for a comprehensive study of pyrobitumen and sulfide arsenic ores focusing mainly on organic matter.The sequentially extracted precious metal content of pyrobitumen reaches up to 7 ppm gold and other metals like Ag 4 ppm,Pt 31 ppb,and Pd 26 ppb,forming metal–organic compounds,while arsenic sulfide minerals incorporate 11 ppm gold,39 ppm Ag,0.49 ppm Pt.The enrichment of gold associating with organic matter and sulfide ore minerals was confirmed in this study.Organic matter was active in the migration of gold and the capture of gold by pyrobitumen.Moreover,the reductive organic matter agent released gold,most likely for the sulfide arsenic ore minerals.Pyrobitumen was a decisive factor in the concentration,transportation,and preservation of gold in the deposit.

AB_(2)-type rare earth-based compounds with C-15 structure:Looking for reversible hydrogen storage materials

AB_(2)-type(A=rare earth,B=transition metal)intermetallic compounds with C15 structure can easily absorb large amount of hydrogen,showing their potential use as hydrogen storage materials.The crucial problem hindering their application is hydrogen induced amorphization(HIA),which leads to the irreversible hydrogen sorption process.The stability of the AB_2 Laves phase compounds,the structural properties,the hydrogenation properties and the controlling factors of HIA are discussed in this review.Comparing with other factors,the atomic radii ratio r_A/r_B is the most important one influencing the HIA.Multi-element substitution is an efficient way to suppress or limit HIA and may enable AB_2 compounds to be suitable for hydrogen storage.

Ligand controlled structure of cadmium(Ⅱ) metal-organic frameworks for fluorescence sensing of Fe^(3+) ion and nitroaromatic compounds

Three cadmium(II) metal-organic frameworks(MOFs) based on tetracarboxylate ligands, namely[Cd_2(TTTA)(DMF)_3]·2 DMF(1),[Cd_2(TB)(H_2O)_4]·3DMF·H_2O(2)and [Cd(TEB)_(0.5)].2 DMF.4 H_2O(3) have been designed and synthesized. Complex 1 is a 2-dimensional(2 D) 3,4-connected network with 3,4 L13 topology, complex 2 features a 3-dimensional(3D) 3,4-connected tfa topology with a 2-fold interpenetrating structure and complex 3 has a 3D 4-connected dia topology with a 4-fold interpenetrating structure. Interestingly, 2 exhibits permanent pores and selective adsorption of CO_2 over CH_4. In addition, 2 shows fluorescence sensing of Fe^(3+) ion and rapid detection of nitroaromatic compounds(NACs) through fluorescence quenching.

Synthesis and DFT Calculation of a Four- coordinated Manganese Compound Mn_2(BPTC)

A new four-coordinated manganese compound Mn2（BPTC） （BPTC =- biphenyl- 2,4,4＇,6-tetracarboxylate） with flu topology net was synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis confirms its crystal belongs to the monoclinic system, space group C2/c with a = 12.2092（11）, b = 14.6932（9）, c = 8.9998（10） A, t= 108.256（12）°, Z= 4, V= 1533.2（2） A3, Dc = 1.889 mg/m3,μ = 1.69, F（O00） = 864, the final R = 0.063 and wR = 0.201 for 1407 observed reflections （I 〉 20（/））. UV-Vis absorption spectrum shows the title compound has a strong absorption at 326 and 238 nm and the optical diffuse reflectance determination shows the band gap of the title compound is 3.15 eV. The theory calculation elucidated that the UV absorptions of the title compound mainly arise from the electron transition from bonding orbitals of BPTC4- ligand to the empty orbitals of BPTC4- and Mn（II） ions.

Core-shell Prussian blue analogues derived from metal-organic frameworks as efficient electrocatalysts for oxygen evolution reaction

Developing high-performance and low-cost electrocatalysts for oxygen evolution reaction(OER)is still a great challenge for water-splitting technologies.Herein,an innovative metal-organic frameworks(MOFs)hybrid-assisted strategy is reported to synthesize core-shell Co/Mn-ZIF@Fe-Co-Mn Prussian blue analogues(PBAs)toward highly efficient OER electrocatalysts in alkaline electrolyte.Physical characterization indicates that the amorphous hydroxide transformed from Co/Mn-ZIF@Fe-Co-Mn PBA(ZIF:zeolitic imidazolate frameworks)during the electrochemical process acted as the electroactive species.Benefiting from these structural and compositional features,the developed composite delivers a remarkably low overpotential of 270 mV with a current density of 10 mA·cm^(−2)in 1.0 M KOH solution.Moreover,water splitting is catalyzed to reach a current density of 10 mA·cm^(−2)at 1.62 V.

Rational design of an AIE-active metal-organic framework for highly sensitive and portable sensing nitroaromatic explosives

Herein,we report a new metal-organic framework with an AIE ligand (H_(4)TCPP=2,3,5,6-tetra-(4-carboxyphenyl)pyrazine) and Mg^(2+) ions,that is,[Mg_(2)(H_(2)O)_(4)TCPP]·DMF·5CH_(3)CN (Mg-TCPP,TCPP=tetra-(4-carboxyphenyl)pyrazine) for detection of nitroaromatic explosives.Due to the coordination effect and restricted intramolecular rotation,Mg-TCPP exhibits bright blue light.As a fluorescent sensor,Mg-TCPP exhibits high selectivity and sensitivity for sensing 2,4,6-trinitrophenol (TNP) by quenching behaviors with the Stern-Volmer quenching constant (K_(SV)) of 3.63×10^(5)L/mol and achieves the low limit of detection of 25.6 ppb,which is beyond most of the previously reported fluorescent materials.Notably,the portable Mg-TCPP films are prepared and it can be used for rapid and sensitive TNP detection in a variety of environments including organic solvent and aqueous solution.Moreover,TNP vapor can be detected within 3 min by naked eye and the film could be regenerated under simple solvent cleaning.

高分散Pd/Ni-A-CA纳米催化剂催化喹啉加氢

以镍(Ni)为金属节点,腺嘌呤(A)和柠檬酸(CA)为有机配体,采用溶剂热法制备了非晶态金属有机配合物Ni-A-CA。将Pd Cl2溶液浸渍于载体Ni-A-CA后用NaBH4还原制得高分散的Pd纳米粒子(Pd NPs)催化剂Pd/Ni-A-CA。通过SEM、TEM、XRD、FTIR、XPS、N2吸附-脱附对载体Ni-A-CA[n(Ni)∶n(A)∶n(CA)=2∶1∶1.5]和催化剂3%Pd/Ni-A-CA(3%为Pd的理论负载量,以Ni-A-CA的质量计,下同)进行了表征。结果表明,Pd NPs高度分散在载体Ni-A-CA上,其粒径为(2.2±0.3) nm,且载体与Pd NPs之间存在的强相互作用增强了催化剂的催化性能。在90℃、2 MPa H2条件下,3%Pd/Ni-A-CA催化喹啉加氢反应70 min,喹啉转化率为99.0%,生成1,2,3,4-四氢喹啉选择性>99%。

模板法制备非晶态CoFe(OH)_(x)的电催化材料的研究

开发具有高效、持久活性析氧反应(oxygen evolution reaction,OER)的过渡金属电催化剂对于清洁制氢生产有重要意义。利用模板法制备非晶态的二元金属氢氧化合物CoFe(OH)_(x)。利用X射线粉末衍射仪(XRD)、傅里叶变换红外光谱(FT-IR)、场发射扫描电子显微镜(SEM)、激光拉曼共聚焦显微镜拉曼光谱仪(Raman)对催化剂的相结构和微观形貌等进行表征,标准三电极的电化学系统在饱和N_(2)气氛的1 mol/L KOH碱性溶液中,考察催化剂在析氧反应中催化性能。得益于非晶态结构存在大量缺陷和反应活性位点以及金属间的协同作用,通过电化学测试CoFe(OH)_(x)/65在电流密度在10 mA/cm^(2)下,过电位为288 mV;此外,其稳定运行14 h内无明显削弱,表现出良好的OER稳定性。

无定形NiCoSe电极的碱性电解水析氢性能

采用电沉积法在镍丝网上合成Ni、Co共掺杂的无定形硒化物NiCoSe作为析氢催化剂电极,利用扫描电镜、X射线衍射仪、透射电镜、X射线光电子能谱仪等观察和分析NiCoSe电极的形貌与结构,通过电化学实验测试电极的电催化析氢性能。结果表明,NiCoSe电极表面镶嵌着球形NiCoSe颗粒,无明显裂纹。NiCoSe化合物为无定形状态,能提供更多的低能垒空穴。适当比例的Ni、Co共掺杂可对Se的电子结构进行调控,使催化剂的电子结合能发生偏移,进而增强催化剂对H原子的吸附能力,使NiCoSe析氢催化剂电极具有较高的本征催化活性。在1 mol/L KOH溶液中10 mA/cm2电流密度下,NiCoSe阴极的过电位为83 mV,塔菲尔斜率为108.98 mV/dec,控制反应速率的步骤为催化剂对H原子的吸附过程。在60 h电解后电流密度衰减率小于5%。

Enhanced thermoelectric properties of NbCoSn half-Heuslers through in-situ nanocrystallization of amorphous precursors during the consolidation process

Tailoring nanostructures is a general approach used to obtain enhanced thermoelectric properties for halfHeusler compounds because the wide areas of grain and phase boundaries could be scattering centers that lower lattice thermal conductivity.However,a common fabrication method based on the sintering of crystalline precursors crushed from as-cast alloy ingots has limitations in obtaining a homogeneous microstructure without microsized impurity phases,owing to residual elemental segregation from casting.In this study,we used amorphous NbCoSn alloys as a precursor for the sintered specimen to obtain a homogeneous NbCoSn bulk specimen without microsized impurity phases and segregation,which led to the enhanced Seebeck coefficient due to the high purity of the half-Heusler phase after crystallization.Moreover,superplasticity originating from amorphous features enabled the powders to be largely deformed during the sintering process,even at a low sintering temperature(953 K).This resulted in less oxidation at both,the grain boundary and the interior,as the O diffusion pathway was blocked during the sintering process.As a result,the NbCoSn0.95Sb0.05 specimen using an amorphous precursor exhibited an enhanced zT of 0.7,due to the increase in the power factor and a decrease in lattice thermal conductivity compared to the specimen using a crystalline precursor.

Amorphous NH_(2)-MIL-68 as an efficient electro-and photo-catalyst for CO_(2)conversion reactions

To produce metal-organic framework(MOF)catalysts with both high activity and durability is interesting but challenging.We report an amorphous MOF(NH_(2)-MIL-68),which combines the advantages of(1)a large number of open metal sites,(2)the basic building blocks and connectivity of crystalline NH_(2)-MIL-68,and(3)hierarchically meso-and microporous structure.It exhibits high performances in electrocatalytic reduction of CO_(2)and photochemical cycloaddition of CO_(2)under mild conditions.For the former reaction,the maximum Faradaic efficiency for product formic acid(FEHCOOH)reaches 93.3%with a current density of 34.2 mA·cm^(−2)at^(−2).05 V vs.Ag/Ag+catalyzed by amorphous NH_(2)-MIL-68,while the crystalline NH_(2)-MIL-68 shows FEHCOOH of 67.7%with considerable productions of CO and H_(2)at the same experimental conditions.For the photochemical cycloaddition of CO_(2)with styrene oxide,the yield by amorphous NH_(2)-MIL-68 can reach 94.1%at 12 h,which is higher than the reported value under similar conditions.The structure–efficiency relationship of the catalyst for the two reactions was investigated.This work opens up new possibility for designing high-performance MOF and MOF-based catalysts.

Amorphous porous sulfides nanosheets with hydrophilic/aerophobic surface for high-current-density water splitting

The rational construction of electrocatalysts with desired features is significant but challenging for superior water splitting at high current density. Herein, amorphous Co Ni S nanosheets are synthesized on nickel foam(NF) through a facile structure evolution strategy and present advanced performance at high current densities in water splitting. The high catalytic activity can be attributed to the sufficient active sites exposed by the flexible amorphous configuration. Moreover, the hydrophilicity and aerophobicity of a-CoNiS/NF promote surface wettability of the self-supporting electrode and avoid the aggregation of bubbles, which expedites the diffusion of electrolyte and facilitates the mass transfer. As a result, the optimized electrode demonstrates low overpotentials of 289 and 434 m V at 500 m A/cm^(2) under alkaline conditions for hydrogen evolution reaction(HER) and oxygen evolution reaction(OER), respectively. Impressively, an electrolytic water splitting cell assembled by bifunctional a-Co Ni S/NF operates with a low cell voltage of 1.46 V@10 mA/cm^(2) and reaches 1.79 V at 500 mA/cm^(2). The strategy sheds light on a competitive platform for the reasonable design of non-precious-metal electrocatalysts under high current density.

Co/Zn-metal organic frameworks derived functional matrix for highly active amorphous Se stabilization and advanced lithium storage

Lithium-selenium batteries,as an advanced rechargeable battery system,have attracted wide attention.However,its application is hurdled by the ambiguous underlying mechanism such as the unclear active phase and the key role of the host materials.Herein,a three-dimensional(3D) functional matrix derived from the Co/Znmetal organic framework is synthesized to unravel the questions raised.It reveals that the strong interaction and voids in the 3D matrix serve to anchor the amorphous Se with high electrochemical properties.The obtained 3DC/Se exhibits 544.2 and 273.2 mAh·g^(-1) t current densities of 0.1C and 2.0C,respectively,with a diffusion-controlled mechanism.The excessive amount of Se beyond the loading capacity of the matrix leads to the formation of trigonal phase Se,which shows an unsatisfying electrochemical property.

Activating coordinative conjugated polymer via interfacial electron transfer for efficient CO_(2) electroreduction

With tunable local electronic environment,high mass density of MN4sites,and ease of preparation,metal-organic conjugated coordinative polymer(CCP) with inherent electronic conductivity provides a promising alternative to the well-known M-N-C electrocatalysts.Herein,the coordination reaction between Cu^(2+)and 1,2,4,5-tetraaminobenzene(TAB) was conducted on the surface of metallic Cu nanowires,forming a thin layer of CuN4-based CCP(Cu-TAB) on the Cu nanowire.More importantly,interfacial transfer of electrons from Cu core to the CuN4-based CCP nanoshell was observed within the resulting CuTAB@Cu,which was found to enrich the local electronic density of the CuN4sites.As such,the CuTAB@Cu demonstrates much improved affinity to the*COOH intermediate formed from the rate determining step;the energy barrier for C-C coupling,which is critical to convert CO_(2)into C2products,is also decreased.Accordingly,it delivers a current density of-9.1 mA cm^(-2)at a potential as high as 0.558 V(vs.RHE) in H-type cell and a Faraday efficiency of 46.4% for ethanol.This work emphasizes the profound role of interfacial interaction in tuning the local electronic structure and activating the CuN4-based CCPs for efficient electroreduction of CO_(2).

Preparation of Ionic Liquids Immobilized on FMIL-101 Catalysts for Conversion of CO_(2)to Propylene Carbonate

Metal-organic frameworks(MOFs)have attracted considerable research attention as a new type of porous material for catalytic applications.Herein,2,5-dihydroxyterephthalic acid was proposed to replace conventional terephthalic acid and reacted with chromic nitrate nonahydrate to synthesize a functional metal–organic framework(FMIL-101).This was then used to immobilize various compound ionic liquids to prepare three ionic liquids immobilized on FMIL-101 catalysts,namely,FMIL-101-[HeMIM]Cl/(ZnBr_(2))_(2),FMIL-101-[CeMIM]Cl/(ZnBr_(2))_(2),and FMIL-101-[AeMIM]Br/(ZnBr_(2))_(2).After characterization by Fourier-transform infrared spectroscopy,X-ray diffraction,ultraviolet spectroscopy,thermogravimetry,specific surface area analysis,and scanning electron microscopy,the catalysts were used to mediate cycloaddition reactions between carbon dioxide(CO_(2))and propylene oxide.The effects of reaction temperature,reaction pressure,reaction time,and catalyst dosage on the catalytic performance were investigated.The results revealed that the FMIL-101-supported CIL catalysts afforded the target product propylene carbonate with good catalytic performance and thermal stability.The optimal catalyst,FMIL-101-[CeMIM]Cl/(ZnBr_(2))_(2),displayed a propylene oxide conversion of 98.64%and a propylene carbonate selectivity of 96.63%at a reaction temperature of 110℃,a reaction pressure of 2.0 MPa,a catalyst dosage of 2.0%relative to propylene oxide,and a reaction time of 2.5 h.In addition,the conversion and selectivity of the catalyst decreased slightly after four cycles.Additionally,the catalyst decreased slightly in catalytic performance after being recycled four times.