Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to ...Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.展开更多
Rational design of organic structure-directing agents(OSDAs)is always regarded as a promising strategy to produce ZSM-48 with diverse configurations.However,to date,only OSDAs with alkyl and alkenyl groups have been e...Rational design of organic structure-directing agents(OSDAs)is always regarded as a promising strategy to produce ZSM-48 with diverse configurations.However,to date,only OSDAs with alkyl and alkenyl groups have been employed to produce ^(*)MRE zeolites with different structures.Aromatic heterocyclic groups were rarely considered for the synthesis of ZSM-48 with a unique nanostructure.In this work,a triazine-based bolaform quaternary ammonium bifunctional template was designed for the first time to fabricate nanorod stacked hierarchical ZSM-48(NSH-ZSM-48).Nanorod-stacked ZSM-48 with different SiO_(2)/Al_(2)O_(3) ratios ranging from 100 to 500 was obtained via a conventional procedure,using the synthesized s-triazine based OSDA,and a reasonable formation mechanism was proposed based on geometrical matching.We also demonstrated that the ZSM-48 nanorods piled up to form an ordered bird’s nest-like hollow sphere configuration.The synthesized NSH-ZSM-48 possesses abundant mesopores and a high surface area,attributed to the SDA’s mesopore-forming and nanonrod’s stacking abilities.In contrast to conventional materials,1 wt%Pd/NSH-ZSM-48 experiences a dramatic increase in the conversion(3.59%)and selectivity(95.7%)of a cyclohexanol/cyclohexanone mixture in the selective oxidation of cyclohexane,which are higher than those for silicalite-1 and SBA-15 with the same loading(2.11%/66.1%and 1.76%/68.5%,respectively).展开更多
Non-surfactant diquaternary ammonium compounds have already been used for obtaining various zeolites in nanocrystalline form. However, facile synthesis of nanocrystals of mordenite (MOR) and beta (BEA) in this way rem...Non-surfactant diquaternary ammonium compounds have already been used for obtaining various zeolites in nanocrystalline form. However, facile synthesis of nanocrystals of mordenite (MOR) and beta (BEA) in this way remains challenging. Here, we present the direct synthesis of nanosized mordernite (MOR) and beta (BEA) zeolites with hexane- and p-xylene-bridged bis-methylpyrrolidinium, -methylpiperidinium and -DABCO diquats, which can be synthesized in a single step from common chemicals. Optimized recipes are presented for nanosized MOR (20–50 nm) and BEA (15–30 nm) zeolites. By investigating the solid products obtained during hydrothermal synthesis, the formation of nanocrystals can be linked to the strong interaction between diquat templates and aluminosilicate species during the induction stage, which limits the amorphous precursor particles to a size below 50 nm. Based on the textural and acidic properties, catalytic performance data are discussed evidencing the clear benefits of these nanosized zeolites over bulk reference samples in Friedel–Crafts reactions and n-alkane hydroconversion.展开更多
We report a computational study of the distribution of germanium ions among the double four-membered rings(D4Rs)in SCM-14 germanosilicate and the influence of a structure-directing agent(SDA)on the stability of the as...We report a computational study of the distribution of germanium ions among the double four-membered rings(D4Rs)in SCM-14 germanosilicate and the influence of a structure-directing agent(SDA)on the stability of the as-synthesized material.For the pure zeolite structure,the calculations suggested clustering of Ge ions and the formation of D4Rs populated entirely by Ge heteroatoms,while part of the D4Rs contain only Si as T-atoms.As a general trend,structures with more Ge–O–Ge bridges are more stable.展开更多
Advanced solid-state NMR techniques,including PT-J-HMQC ^(27)Al/^(31)P double-resonance NMR,2D ^(31)P and 1H DQ-SQ MAS NMR experiments,have been used to study the structure-directing effect in the crystallization of t...Advanced solid-state NMR techniques,including PT-J-HMQC ^(27)Al/^(31)P double-resonance NMR,2D ^(31)P and 1H DQ-SQ MAS NMR experiments,have been used to study the structure-directing effect in the crystallization of the molecular sieve AlPO_(4) -11 synthesized by a solvent-free method.展开更多
Recently,organic-inorganic hybrid lead halides have been explored as photoluminescent(PL)materials with flexible structural tunabilities and high photoluminescence quantum efficiencies,which can be modified by the str...Recently,organic-inorganic hybrid lead halides have been explored as photoluminescent(PL)materials with flexible structural tunabilities and high photoluminescence quantum efficiencies,which can be modified by the structure regulating functions of organic cations.Here,by adopting different saturated organic cations as structure directing agents(SDAs),a series of organic-inorganic hybrid lead halides have been solvothermally synthesized and characterized with different structural types.Compound[(CH_(3))_(2)NH_(2)]_(2)[H_(2)DABCO]_(2)Pb_(3)I_(12)(1,DABCO=1,4-diazabicyclo[2.2.2]-octane)features a linear zerodimensional(0D)[Pb_(3)I_(12)]_(6)-trimer,and[(Me)_(6)-en]_(2)Pb_(3)I_(10)(2)and[H_(2)N-Prpipz]_(2)Pb_(3)Br_(10)(3)contain two different types of one-dimensional(1D)[Pb_(3)X_(10)]_(4)-chains based on the C_(3)-symterric[Pb_(3)X11]trimer and[PbX_(6)]unit,respectively.In the structures of H[(Me)_(2)-DABCO]Pb_(3)I_(9)(4)and H[(Me)4-pipz]Pb_(3)I_(9)(5,pipz=piperazine),the C_(3)-symmetric[Pb_(3)I_(11)]trimers are interlinked to form the same two-dimensional(2D)corrugated[Pb_(3)I_(9)]^(3-)layers.Under the excitation of UV irradiation,these hybrid lead halides exhibit tunable luminescence properties from yellow,orange to red emissions with the largest Stokes shift of 335 nm.The PL nature is also investigated based on temperature-dependent PL emission,time-resolved PL and theoretical calculations,etc.These hybrid lead halides provide new types of structural models to probe into the PL properties and understand the underlying structure-property relationship.展开更多
Curcurbit[n]uril(Q[n])-based supramolecular frameworks(QSFs) constructed from the outer surface interaction of Q[n]s(OSIQ) have the characteristic of simplicity,diversity and modulability.Their simplicity is reflected...Curcurbit[n]uril(Q[n])-based supramolecular frameworks(QSFs) constructed from the outer surface interaction of Q[n]s(OSIQ) have the characteristic of simplicity,diversity and modulability.Their simplicity is reflected in their simple composition and preparation methods used for QSFs.The diversity of supramolecular organic frameworks(SOFs) is reflected in the synthesis methods and structural characteristics of the as-obtained QSFs,as well as the variety of structural directing agents and basic building blocks used to prepare QSFs.The modulability is reflected by the controllable channel size in the QSFs,which can be adjusted using different sizes of Q[n]s.In this work,the first re ported cucurbituril Q[6]was selected as the basic building block and three Q[6]-based su p ramolecular frameworks were obtained from aqueous HCl solutions in the presence of [CdCl_(4)]^(2-)respectively.The OSIQs are the main driving forces for the formation of these frameworks.This study shows the diversity of the QSFs.展开更多
A typical zeolite synthesis reaction mixture involves a framework atom source,a solvent,a mineraliser,and a structure directing agent.However,these components often have a dual function,and their impact on the nucleat...A typical zeolite synthesis reaction mixture involves a framework atom source,a solvent,a mineraliser,and a structure directing agent.However,these components often have a dual function,and their impact on the nucleation/crystallization process is difficult to establish straightforwardly.The present study deals with the structure directing effect of zinc on the preparation of zincosilicate RUB-17(RSN-type material).First,an attempt was made to introduce several other heteroatoms(Al,B,Ge,Mg,Li,and Zr)into the RSN framework under the same reaction conditions as those for Zn-RSN.Second,different Zn sources have been employed in order to study their impact on RUB-17 intermediates and the final product properties.The obtained series of samples were analysed by XRD,XRF,GISAXS,SEM,TEM,and TG as well as by Raman,NMR,infrared and solid state UV/VIS spectroscopy.The physicochemical analysis of the obtained solids was complemented by DFT modelling.The results show that a RSN-type material can be solely prepared in the Zn-containing systems,where zinc plays a structure directing role besides its function as a framework cation.Namely,the lov-unit,a basic building unit of the RSN framework,is formed at the very beginning of the crystallization no matter the zinc source employed.Yet,the differences in the crystallization of different systems and relatively long time needed for full transformation of the precursor indicate that there is some other limiting step that accounts for the formation of zeolites.展开更多
UiO-66,reported in 2008,inspired the ongoing chemistry of group 4 metal–organic frameworks and it is still one of the most studied MOFs due to its exceptional stability.The tightness of their building blocks and bond...UiO-66,reported in 2008,inspired the ongoing chemistry of group 4 metal–organic frameworks and it is still one of the most studied MOFs due to its exceptional stability.The tightness of their building blocks and bond strength make it tough to access new topologies,unless the building blocks are changed or defect engineering is employed,which in turn lead to different nominal stoichiometries.However,well selected structure directing agents and harsh synthesis conditions allowed the isolation of the first polymorph of UiO-66,named EHU-30.Herein,we provide evidence for the generalization of the synthetic approach with four new EHU-30 isoreticular compounds,based on amino-functionalized linkers and zirconium and hafnium as metal centres:EHU-30-NH_(2)(M)and EHU-30-NHR(M)(M:Zr,Hf;R:2-carboxypropyl).The crystal structure analysis reveals that their framework is more porous than that of their polymorphic counterpart.Furthermore,due to the current relevance of MOFs in greenhouse gas capture and in water harvesting methodologies,we have explored CO_(2)and water vapour adsorption on the new polymorphic phases,by means of experimental and computational resources,and compared to the parent EHU-30.The amino functionalization makes the EHU-30 series more prone to CO_(2)and water vapour adsorption.Besides,the water adsorption isotherms show an interesting crossing sensitive to temperature,sorption cycles and functionalization of the linker,which has been attributed to a localized structural transformation from EHU-30 to UiO-66.Finally,time-of-flight(TOF)powder neutron diffraction experiments were also conducted to locate the preferred adsorption sites for water in functionalized and parent EHU-30 structures.展开更多
A facile hydrothermal etching–healing strategy is proposed to fabricate a Sn-MWW zeolite based on a pure silica ITQ-1 precursor,which avoids using any supporting agents and additives,such as B^(3+) and Na^(+). Thus,p...A facile hydrothermal etching–healing strategy is proposed to fabricate a Sn-MWW zeolite based on a pure silica ITQ-1 precursor,which avoids using any supporting agents and additives,such as B^(3+) and Na^(+). Thus,post-synthetic acid treatments for the removal of such additives to ensure catalytic performance are not required,which is a great improvement to the conventional Sn-MWW synthetic route. Moreover,low organic structure-directing agent (SDA) consumption and rapid growth make this approach practically attractive. The growth mechanism study reveals the crucial etching and healing dual functional role of the SDA,which leads to successful Sn introduction. The obtained Sn-MWW exhibits excellent glucose isomerization catalytic performance owing to the “clean” (without the side effect of additives) and well-defined Sn sites.展开更多
Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine(MMA)and dimethylamine(DMA)through the reaction of methanol(MeOH)with ammonia.However,they t...Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine(MMA)and dimethylamine(DMA)through the reaction of methanol(MeOH)with ammonia.However,they typically suffer from rapid deactivation.Herein,we report the synthesis of highsilica RHO zeolite with small crystal sizes(1-2μm)via interzeolite conversion of SSZ-13,utilizing a reduced amount of organic structure-directing agent(OSDA)and without the use of fluoride.It was demonstrated that the double eight-membered rings of RHO zeolite can be formed using the single eight-membered ring of SSZ-13,resulting in a reduction of OSDA dosage by approximately 30%and Cs^(+)by about 38%.The resulting high-silica RHO zeolites exhibit an excellent methanol conversion of∼93%,a high MMA and DMA yield of∼90%,and good reaction durability under conditions more severe than those of industrial manufacture conditions,at 350℃with a liquid hourly space velocity at 11.7 h^(−1).Compared to directly synthesized high-silica RHO zeolites with larger crystal sizes(3-8μm),interzeolite-converted high-silica RHO zeolites with smaller crystal sizes show a 10-16%higher yield of MMA and DMA.These findings highlight the significant potential of high-silica RHO zeolites for the industrial manufacturing of MMA and DMA.展开更多
Zeolites are widely recognised as effective adsorbents for the removal of organic pollutants from aqueous sources.However,their intrinsic powder form makes their application restricted by the arduous filtrationrecover...Zeolites are widely recognised as effective adsorbents for the removal of organic pollutants from aqueous sources.However,their intrinsic powder form makes their application restricted by the arduous filtrationrecovery process and their decreased activity due to aggregation.Herein,we report the organic structure directing agent(OSDA)free and binder-free preparation of ZSM-5@silica beads for organic pollutant sequestration exemplified by the aniline removal.All silica beads were prepared by employing ion exchange resin beads as a macro-template and further used to prepare a ZSM-5@silica composite.First,anion exchange resin beads were charged with silica by ion exchange.Second,the anion exchange resin was eliminated by high temperature combustion leaving behind an all-silica replica.The all-silica replica was partially transformed into ZSM-5 by hydrothermal treatment.ZSM-5 was synthesized from the OSDA-free system,thus avoiding high temperature calcination of the composite.The effect of the crystallization temperature(120,150,and 170℃)on the formation of ZSM-5 was studied.The physicochemical properties of the obtained beads were determined using different characterization methods such as powder X-ray diffraction(XRD),scanning-electron microscopy(SEM),N_(2)adsorption–desorption isotherms,and thermogravimetry(TG).The ZSM-5@silica composite demonstrated a remarkable capacity,outpacing most silica-based adsorbents and modified zeolitic materials,re-usability and retained spherical shape.The binder-free zeolite shaping technology offers a green and straightforward method for preparing zeolite-based adsorbents for the removal of organic pollutants from waste water.展开更多
Cu-SSZ-13(CHA topology)zeolites are commonly used in diesel engines for the selective catalytic reduction(NH3-SCR)of nitrogen oxides(NO_(x)).However,their synthesis typically requires long crystallization times and th...Cu-SSZ-13(CHA topology)zeolites are commonly used in diesel engines for the selective catalytic reduction(NH3-SCR)of nitrogen oxides(NO_(x)).However,their synthesis typically requires long crystallization times and their durability in NH3-SCR is limited.Herein,we achieved a significant reduction in crystallization time,synthesizing SSZ-13 zeolites in just 6 h by using SAPO-18 seeds and a minimal amount of an organic structure-directing agent(OSDA).The OSDA/Si ratio was reduced by a factor of 16 compared to conventional methods.Crystallization studies revealed that SAPO-18 seeds promoted the formation of four-membered rings(4MRs),which quickly combined into double 6-membered rings(D6Rs)with the assistance of the OSDA,enabling rapid crystallization of SSZ-13.The resulting Cu-SSZ-13 demonstrated comparable NH3-SCR performance to conventionally synthesized Cu-SSZ-13(Cuconv-SSZ-13).Moreover,we introduced Ce ions into Cu-SSZ-13 to enhance its hydrothermal stability and explored the effects of different metal precursors on the catalytic performance.The optimized CuCe(Ⅲ)0.5-SSZ-13 exhibited superior hydrothermal stability compared to Cu-SSZ-13.Conversely,CuCe(Ⅳ)1.0-SSZ-13 and CuCe(Ⅲ)0.5Ce(Ⅳ)1.0-SSZ-13 displayed reduced hydrothermal stability.Characterization revealed that using the Ce(Ⅲ)precursor inhibited CuO_(x) formation during hydrothermal ageing,while the Ce(Ⅳ)precursor favored the formation of CeO2,decreasing the zeolite stability and promoting CuO_(x) formation.This work presents a novel approach for rapid SSZ-13 synthesis and highlights the critical role of metal precursors in the performance of bimetallic SSZ-13 zeolites.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.21802136)~~
文摘Zeolite synthesis in contemporary chemical industries is predominantly conducted using organic structure‐directing agents(OSDAs),which are chronically hazardous to humans and the environment.It is a growing trend to develop an eco‐friendly and nuisanceless OSDA for zeolite synthesis.Herein,choline is employed as a non‐toxic and green OSDA to synthesize high silica Y zeolite with SiO2/Al2O3 ratios of 6.5–6.8.The prepared Y zeolite samples exhibited outstanding(hydro)thermal stability at ultrahigh temperature owing to the higher SiO2/Al2O3 ratio.The XRF,SEM,29Si‐NMR and 13Na+results suggested that choline plays a structure‐directing role in the synthesis of Y zeolite,while the feed molar fraction of Na+is a crucial determinant for the framework SiO2/Al2O3 ratio and the crystal morphology.
基金financially supported by the National Natural Science Foundation of China(21776311 and 22102215)Taishan Scholar Foundation(tspd20210308)+3 种基金the“111”Program of National College Disciplinary Innovation(B13031)Shandong Provincial Natural Science Foundation,China(ZR2019MB045 and ZR2019MB022)the National Key Technologies R&D Program of China,the Key Projects of Intergovernmental International Innovation Cooperation(2018YFE0118200)the Key Research and Development Project of Shandong province(2019JZZY010506).
文摘Rational design of organic structure-directing agents(OSDAs)is always regarded as a promising strategy to produce ZSM-48 with diverse configurations.However,to date,only OSDAs with alkyl and alkenyl groups have been employed to produce ^(*)MRE zeolites with different structures.Aromatic heterocyclic groups were rarely considered for the synthesis of ZSM-48 with a unique nanostructure.In this work,a triazine-based bolaform quaternary ammonium bifunctional template was designed for the first time to fabricate nanorod stacked hierarchical ZSM-48(NSH-ZSM-48).Nanorod-stacked ZSM-48 with different SiO_(2)/Al_(2)O_(3) ratios ranging from 100 to 500 was obtained via a conventional procedure,using the synthesized s-triazine based OSDA,and a reasonable formation mechanism was proposed based on geometrical matching.We also demonstrated that the ZSM-48 nanorods piled up to form an ordered bird’s nest-like hollow sphere configuration.The synthesized NSH-ZSM-48 possesses abundant mesopores and a high surface area,attributed to the SDA’s mesopore-forming and nanonrod’s stacking abilities.In contrast to conventional materials,1 wt%Pd/NSH-ZSM-48 experiences a dramatic increase in the conversion(3.59%)and selectivity(95.7%)of a cyclohexanol/cyclohexanone mixture in the selective oxidation of cyclohexane,which are higher than those for silicalite-1 and SBA-15 with the same loading(2.11%/66.1%and 1.76%/68.5%,respectively).
文摘Non-surfactant diquaternary ammonium compounds have already been used for obtaining various zeolites in nanocrystalline form. However, facile synthesis of nanocrystals of mordenite (MOR) and beta (BEA) in this way remains challenging. Here, we present the direct synthesis of nanosized mordernite (MOR) and beta (BEA) zeolites with hexane- and p-xylene-bridged bis-methylpyrrolidinium, -methylpiperidinium and -DABCO diquats, which can be synthesized in a single step from common chemicals. Optimized recipes are presented for nanosized MOR (20–50 nm) and BEA (15–30 nm) zeolites. By investigating the solid products obtained during hydrothermal synthesis, the formation of nanocrystals can be linked to the strong interaction between diquat templates and aluminosilicate species during the induction stage, which limits the amorphous precursor particles to a size below 50 nm. Based on the textural and acidic properties, catalytic performance data are discussed evidencing the clear benefits of these nanosized zeolites over bulk reference samples in Friedel–Crafts reactions and n-alkane hydroconversion.
文摘We report a computational study of the distribution of germanium ions among the double four-membered rings(D4Rs)in SCM-14 germanosilicate and the influence of a structure-directing agent(SDA)on the stability of the as-synthesized material.For the pure zeolite structure,the calculations suggested clustering of Ge ions and the formation of D4Rs populated entirely by Ge heteroatoms,while part of the D4Rs contain only Si as T-atoms.As a general trend,structures with more Ge–O–Ge bridges are more stable.
基金supported by the National Key Research and Development Program of China (2017YFB0702803)the National Natural Science Foundation of China (91545111, 91634201, 21773296, 21573282 and 21733013).
文摘Advanced solid-state NMR techniques,including PT-J-HMQC ^(27)Al/^(31)P double-resonance NMR,2D ^(31)P and 1H DQ-SQ MAS NMR experiments,have been used to study the structure-directing effect in the crystallization of the molecular sieve AlPO_(4) -11 synthesized by a solvent-free method.
基金support from the National Nature Science Foundation of China(No.21571081,21671080 and 21601181)Fund of State Key Laboratory of Structural Chemistry(No.20170011)+2 种基金a Project of Shandong Province Higher Educational Science and Technology Program(J18kz005)Laboratory Open Foundation of Qufu Normal University(sk201722)the Cultivating Project for Talent Team and Ascendant Subject of University in Shandong Province.
文摘Recently,organic-inorganic hybrid lead halides have been explored as photoluminescent(PL)materials with flexible structural tunabilities and high photoluminescence quantum efficiencies,which can be modified by the structure regulating functions of organic cations.Here,by adopting different saturated organic cations as structure directing agents(SDAs),a series of organic-inorganic hybrid lead halides have been solvothermally synthesized and characterized with different structural types.Compound[(CH_(3))_(2)NH_(2)]_(2)[H_(2)DABCO]_(2)Pb_(3)I_(12)(1,DABCO=1,4-diazabicyclo[2.2.2]-octane)features a linear zerodimensional(0D)[Pb_(3)I_(12)]_(6)-trimer,and[(Me)_(6)-en]_(2)Pb_(3)I_(10)(2)and[H_(2)N-Prpipz]_(2)Pb_(3)Br_(10)(3)contain two different types of one-dimensional(1D)[Pb_(3)X_(10)]_(4)-chains based on the C_(3)-symterric[Pb_(3)X11]trimer and[PbX_(6)]unit,respectively.In the structures of H[(Me)_(2)-DABCO]Pb_(3)I_(9)(4)and H[(Me)4-pipz]Pb_(3)I_(9)(5,pipz=piperazine),the C_(3)-symmetric[Pb_(3)I_(11)]trimers are interlinked to form the same two-dimensional(2D)corrugated[Pb_(3)I_(9)]^(3-)layers.Under the excitation of UV irradiation,these hybrid lead halides exhibit tunable luminescence properties from yellow,orange to red emissions with the largest Stokes shift of 335 nm.The PL nature is also investigated based on temperature-dependent PL emission,time-resolved PL and theoretical calculations,etc.These hybrid lead halides provide new types of structural models to probe into the PL properties and understand the underlying structure-property relationship.
基金the financial support of the National Natural Science Foundation of China(Nos.21761007,51663005 and 21871064)Science and Technology Plan Project of Guizhou Province(Nos.20175788 and 20185781)。
文摘Curcurbit[n]uril(Q[n])-based supramolecular frameworks(QSFs) constructed from the outer surface interaction of Q[n]s(OSIQ) have the characteristic of simplicity,diversity and modulability.Their simplicity is reflected in their simple composition and preparation methods used for QSFs.The diversity of supramolecular organic frameworks(SOFs) is reflected in the synthesis methods and structural characteristics of the as-obtained QSFs,as well as the variety of structural directing agents and basic building blocks used to prepare QSFs.The modulability is reflected by the controllable channel size in the QSFs,which can be adjusted using different sizes of Q[n]s.In this work,the first re ported cucurbituril Q[6]was selected as the basic building block and three Q[6]-based su p ramolecular frameworks were obtained from aqueous HCl solutions in the presence of [CdCl_(4)]^(2-)respectively.The OSIQs are the main driving forces for the formation of these frameworks.This study shows the diversity of the QSFs.
基金Croatian Science Foundation,project number O-2594-2018supported by the University of Rijeka under the project number 13.2.1.3.04.
文摘A typical zeolite synthesis reaction mixture involves a framework atom source,a solvent,a mineraliser,and a structure directing agent.However,these components often have a dual function,and their impact on the nucleation/crystallization process is difficult to establish straightforwardly.The present study deals with the structure directing effect of zinc on the preparation of zincosilicate RUB-17(RSN-type material).First,an attempt was made to introduce several other heteroatoms(Al,B,Ge,Mg,Li,and Zr)into the RSN framework under the same reaction conditions as those for Zn-RSN.Second,different Zn sources have been employed in order to study their impact on RUB-17 intermediates and the final product properties.The obtained series of samples were analysed by XRD,XRF,GISAXS,SEM,TEM,and TG as well as by Raman,NMR,infrared and solid state UV/VIS spectroscopy.The physicochemical analysis of the obtained solids was complemented by DFT modelling.The results show that a RSN-type material can be solely prepared in the Zn-containing systems,where zinc plays a structure directing role besides its function as a framework cation.Namely,the lov-unit,a basic building unit of the RSN framework,is formed at the very beginning of the crystallization no matter the zinc source employed.Yet,the differences in the crystallization of different systems and relatively long time needed for full transformation of the precursor indicate that there is some other limiting step that accounts for the formation of zeolites.
基金the financial support from the Basque Government(IT1291-19)from the Spanish Ministry of Science and Innovation(PID2019-108028GB-C21,CTQ2017-92173-EXP and IJC2018-038162-I)+2 种基金Technical and human support provided by SGIker(UPV/EHU,MICINN,GV/EJ,and ESF)HPC support from C3UPO are also acknowledgedthe ISIS Neutron and Muon Source for the award of beam time on GEM(experiment RB1920440).
文摘UiO-66,reported in 2008,inspired the ongoing chemistry of group 4 metal–organic frameworks and it is still one of the most studied MOFs due to its exceptional stability.The tightness of their building blocks and bond strength make it tough to access new topologies,unless the building blocks are changed or defect engineering is employed,which in turn lead to different nominal stoichiometries.However,well selected structure directing agents and harsh synthesis conditions allowed the isolation of the first polymorph of UiO-66,named EHU-30.Herein,we provide evidence for the generalization of the synthetic approach with four new EHU-30 isoreticular compounds,based on amino-functionalized linkers and zirconium and hafnium as metal centres:EHU-30-NH_(2)(M)and EHU-30-NHR(M)(M:Zr,Hf;R:2-carboxypropyl).The crystal structure analysis reveals that their framework is more porous than that of their polymorphic counterpart.Furthermore,due to the current relevance of MOFs in greenhouse gas capture and in water harvesting methodologies,we have explored CO_(2)and water vapour adsorption on the new polymorphic phases,by means of experimental and computational resources,and compared to the parent EHU-30.The amino functionalization makes the EHU-30 series more prone to CO_(2)and water vapour adsorption.Besides,the water adsorption isotherms show an interesting crossing sensitive to temperature,sorption cycles and functionalization of the linker,which has been attributed to a localized structural transformation from EHU-30 to UiO-66.Finally,time-of-flight(TOF)powder neutron diffraction experiments were also conducted to locate the preferred adsorption sites for water in functionalized and parent EHU-30 structures.
基金supported by the National Natural Science Foundation of China(22002012)the Liaoning Revitalization Talent Program(XLYC2008032)the Fundamental Research Funds for the Central Universities(DUT21LK24).
文摘A facile hydrothermal etching–healing strategy is proposed to fabricate a Sn-MWW zeolite based on a pure silica ITQ-1 precursor,which avoids using any supporting agents and additives,such as B^(3+) and Na^(+). Thus,post-synthetic acid treatments for the removal of such additives to ensure catalytic performance are not required,which is a great improvement to the conventional Sn-MWW synthetic route. Moreover,low organic structure-directing agent (SDA) consumption and rapid growth make this approach practically attractive. The growth mechanism study reveals the crucial etching and healing dual functional role of the SDA,which leads to successful Sn introduction. The obtained Sn-MWW exhibits excellent glucose isomerization catalytic performance owing to the “clean” (without the side effect of additives) and well-defined Sn sites.
基金the National Key Research and Development Program of China(2021YFA1500401,2021YFA1501202,2022YFB3504000)the National Natural Science Foundation of China(22288101,21991091)the‘111 Center’(B17020)for supporting this work.
文摘Low-silica RHO zeolites have been recognized as efficient catalysts for synthesizing industrial intermediates monomethylamine(MMA)and dimethylamine(DMA)through the reaction of methanol(MeOH)with ammonia.However,they typically suffer from rapid deactivation.Herein,we report the synthesis of highsilica RHO zeolite with small crystal sizes(1-2μm)via interzeolite conversion of SSZ-13,utilizing a reduced amount of organic structure-directing agent(OSDA)and without the use of fluoride.It was demonstrated that the double eight-membered rings of RHO zeolite can be formed using the single eight-membered ring of SSZ-13,resulting in a reduction of OSDA dosage by approximately 30%and Cs^(+)by about 38%.The resulting high-silica RHO zeolites exhibit an excellent methanol conversion of∼93%,a high MMA and DMA yield of∼90%,and good reaction durability under conditions more severe than those of industrial manufacture conditions,at 350℃with a liquid hourly space velocity at 11.7 h^(−1).Compared to directly synthesized high-silica RHO zeolites with larger crystal sizes(3-8μm),interzeolite-converted high-silica RHO zeolites with smaller crystal sizes show a 10-16%higher yield of MMA and DMA.These findings highlight the significant potential of high-silica RHO zeolites for the industrial manufacturing of MMA and DMA.
基金Q.F.and V.V.thank the National Natural Science Foundation of China(21571079,21621001,21390394,21571076 and 21571078)for their financial supportThis study was partially supported by the Sino-French International Associated Laboratory“Zeolites”.
文摘Zeolites are widely recognised as effective adsorbents for the removal of organic pollutants from aqueous sources.However,their intrinsic powder form makes their application restricted by the arduous filtrationrecovery process and their decreased activity due to aggregation.Herein,we report the organic structure directing agent(OSDA)free and binder-free preparation of ZSM-5@silica beads for organic pollutant sequestration exemplified by the aniline removal.All silica beads were prepared by employing ion exchange resin beads as a macro-template and further used to prepare a ZSM-5@silica composite.First,anion exchange resin beads were charged with silica by ion exchange.Second,the anion exchange resin was eliminated by high temperature combustion leaving behind an all-silica replica.The all-silica replica was partially transformed into ZSM-5 by hydrothermal treatment.ZSM-5 was synthesized from the OSDA-free system,thus avoiding high temperature calcination of the composite.The effect of the crystallization temperature(120,150,and 170℃)on the formation of ZSM-5 was studied.The physicochemical properties of the obtained beads were determined using different characterization methods such as powder X-ray diffraction(XRD),scanning-electron microscopy(SEM),N_(2)adsorption–desorption isotherms,and thermogravimetry(TG).The ZSM-5@silica composite demonstrated a remarkable capacity,outpacing most silica-based adsorbents and modified zeolitic materials,re-usability and retained spherical shape.The binder-free zeolite shaping technology offers a green and straightforward method for preparing zeolite-based adsorbents for the removal of organic pollutants from waste water.
基金the National Natural Science Foundation of China(22301209,22476147,22288101,22405293)the Zhejiang Province Science Technology Planning Project(no.2021C03023)+1 种基金the Zhejiang Provincial Natural Science Foundation of China(no.ZCLQ24B0101)the‘111 Center’(B17020)for supporting this work.
文摘Cu-SSZ-13(CHA topology)zeolites are commonly used in diesel engines for the selective catalytic reduction(NH3-SCR)of nitrogen oxides(NO_(x)).However,their synthesis typically requires long crystallization times and their durability in NH3-SCR is limited.Herein,we achieved a significant reduction in crystallization time,synthesizing SSZ-13 zeolites in just 6 h by using SAPO-18 seeds and a minimal amount of an organic structure-directing agent(OSDA).The OSDA/Si ratio was reduced by a factor of 16 compared to conventional methods.Crystallization studies revealed that SAPO-18 seeds promoted the formation of four-membered rings(4MRs),which quickly combined into double 6-membered rings(D6Rs)with the assistance of the OSDA,enabling rapid crystallization of SSZ-13.The resulting Cu-SSZ-13 demonstrated comparable NH3-SCR performance to conventionally synthesized Cu-SSZ-13(Cuconv-SSZ-13).Moreover,we introduced Ce ions into Cu-SSZ-13 to enhance its hydrothermal stability and explored the effects of different metal precursors on the catalytic performance.The optimized CuCe(Ⅲ)0.5-SSZ-13 exhibited superior hydrothermal stability compared to Cu-SSZ-13.Conversely,CuCe(Ⅳ)1.0-SSZ-13 and CuCe(Ⅲ)0.5Ce(Ⅳ)1.0-SSZ-13 displayed reduced hydrothermal stability.Characterization revealed that using the Ce(Ⅲ)precursor inhibited CuO_(x) formation during hydrothermal ageing,while the Ce(Ⅳ)precursor favored the formation of CeO2,decreasing the zeolite stability and promoting CuO_(x) formation.This work presents a novel approach for rapid SSZ-13 synthesis and highlights the critical role of metal precursors in the performance of bimetallic SSZ-13 zeolites.
