Metal-organic frameworks(MOFs)have played a pivotal role in catalysis,driven by their remarkable surface areas and structural versatility.The structural manipulation of zeolitic imidazolate frameworks(ZIFs)has shed li...Metal-organic frameworks(MOFs)have played a pivotal role in catalysis,driven by their remarkable surface areas and structural versatility.The structural manipulation of zeolitic imidazolate frameworks(ZIFs)has shed light on the impact of size,facet orientation,and functional groups in enhancing their catalytic performance.However,these strategies possess inherent limitations,necessitating the pursuit of novel avenues.This study introduces an innovative methodology to elucidate the intricate interplay between the ZIF structure and catalytic activity.This involves externally modifying existing ZIF nanocrystals through precise carving,resulting in the creation of heterogeneous porous architectures.Through the chemical etching of core metal nanoparticles within ZIF-8 nanocrystals,the introduction of heterogeneous internal mesoporosity within ZIF-8 emerges,providing effective mass transport and uncoordinated active sites for enhanced heterogeneous catalysis.The effectiveness of this porous inner space is demonstrated through the Knoevenagel condensation reaction.Four different types of ZIF-8 crystal structures undergo evaluation for catalytic activity:pristine ZIF nanocubes,etched ZIF nanocubes,ZIFs with gold nanorod cores,and ZIFs with inner etched spaces.This innovative approach,centered on introducing heterogeneous porosity within ZIF-8,offers promising prospects for the design of ZIF-based catalysts boasting exceptional catalytic efficiency in various organic transformations.展开更多
Metal-organic framework(MOF)nanocrystals with high surface area and morphological tunability have shown great potential for a wide range of industrial applications when compared with their bulk counterparts.However,ac...Metal-organic framework(MOF)nanocrystals with high surface area and morphological tunability have shown great potential for a wide range of industrial applications when compared with their bulk counterparts.However,achieving environment-friendly synthesis of MOF nanocrystals with minimal use of hazardous chemicals and low energy consumption remains a significant challenge.Herein,we developed a soft seed-mediated approach to synthesise nanocrystals of zeolitic imidazolate frameworks(ZIFs)in water without any assistance of chemical additives such as surfactants and organic solvents.An oil-in-water microemulsion,made from a trace amount of oil with water,was introduced to the reaction medium as the soft seed,and precise size control of ZIF-8 crystals from nanometres to micrometres was enabled by varying the volume of the oil-in-water microemulsion.Scanning electron microscopy and cryo-transmission electron microscopy analyses of the reaction intermediates revealed that the surface of the oil-in-water microemulsion functions as a nucleation site for ZIF-8 crystals,which dissipates over time.Furthermore,aromatic compounds with different numbers and lengths of alkyl chains for the oil phase were used to examine the chemical effect of the oil-in-water microemulsion on ZIF-8 crystal size,which led to fine-size control of ZIF-8 nanocrystals.Our microemulsion-induced synthesis could also be used to dimensionally control ZIF-67 crystals as well as ZIF-derived hollow nanostructures.ZIF-8 nanocrystals in our work exhibited enhanced catalytic activity for Knoevenagel condensation and dye adsorptivity with methyl orange and rhodamine B.We anticipate that our soft seed-mediated method will help improve the efficiency of MOF nanocrystal production for industrial applications.展开更多
Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays a...Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions.展开更多
基金supported by the Basic Science Research Program(2020R1C1C1007568 and 2022R1A4A1022252)through the National Research Foundation of Korea and the research grant of the Gyeongsang National University in 2023In addition,this work was partially supported by the KBSI NFEC(2019R1A6C1010042)from the Ministry of Education of Korea and the Korea Institute for Advancement of Technology(P0017310,Human Resource Development Program for Industrial Innovation(global)).
文摘Metal-organic frameworks(MOFs)have played a pivotal role in catalysis,driven by their remarkable surface areas and structural versatility.The structural manipulation of zeolitic imidazolate frameworks(ZIFs)has shed light on the impact of size,facet orientation,and functional groups in enhancing their catalytic performance.However,these strategies possess inherent limitations,necessitating the pursuit of novel avenues.This study introduces an innovative methodology to elucidate the intricate interplay between the ZIF structure and catalytic activity.This involves externally modifying existing ZIF nanocrystals through precise carving,resulting in the creation of heterogeneous porous architectures.Through the chemical etching of core metal nanoparticles within ZIF-8 nanocrystals,the introduction of heterogeneous internal mesoporosity within ZIF-8 emerges,providing effective mass transport and uncoordinated active sites for enhanced heterogeneous catalysis.The effectiveness of this porous inner space is demonstrated through the Knoevenagel condensation reaction.Four different types of ZIF-8 crystal structures undergo evaluation for catalytic activity:pristine ZIF nanocubes,etched ZIF nanocubes,ZIFs with gold nanorod cores,and ZIFs with inner etched spaces.This innovative approach,centered on introducing heterogeneous porosity within ZIF-8,offers promising prospects for the design of ZIF-based catalysts boasting exceptional catalytic efficiency in various organic transformations.
基金supported by the Basic Science Research Program(2020R1C1C1007568 and 2022R1A4A1022252)through the National Research Foundation of Koreathe Korea Institute of Energy Technology Evaluation and Planning(20192050100060)+1 种基金In addition,this work was partially supported by the KBSI NFEC(2019R1A6C1010042)from the Ministry of Education of KoreaKorea Institute for Advancement of Technology(P0017310,Human Resource Development Program for Industrial Innovation(global)).
文摘Metal-organic framework(MOF)nanocrystals with high surface area and morphological tunability have shown great potential for a wide range of industrial applications when compared with their bulk counterparts.However,achieving environment-friendly synthesis of MOF nanocrystals with minimal use of hazardous chemicals and low energy consumption remains a significant challenge.Herein,we developed a soft seed-mediated approach to synthesise nanocrystals of zeolitic imidazolate frameworks(ZIFs)in water without any assistance of chemical additives such as surfactants and organic solvents.An oil-in-water microemulsion,made from a trace amount of oil with water,was introduced to the reaction medium as the soft seed,and precise size control of ZIF-8 crystals from nanometres to micrometres was enabled by varying the volume of the oil-in-water microemulsion.Scanning electron microscopy and cryo-transmission electron microscopy analyses of the reaction intermediates revealed that the surface of the oil-in-water microemulsion functions as a nucleation site for ZIF-8 crystals,which dissipates over time.Furthermore,aromatic compounds with different numbers and lengths of alkyl chains for the oil phase were used to examine the chemical effect of the oil-in-water microemulsion on ZIF-8 crystal size,which led to fine-size control of ZIF-8 nanocrystals.Our microemulsion-induced synthesis could also be used to dimensionally control ZIF-67 crystals as well as ZIF-derived hollow nanostructures.ZIF-8 nanocrystals in our work exhibited enhanced catalytic activity for Knoevenagel condensation and dye adsorptivity with methyl orange and rhodamine B.We anticipate that our soft seed-mediated method will help improve the efficiency of MOF nanocrystal production for industrial applications.
基金the Korea Institute of Energy Technology Evaluation and Planning(No.20192050100060)from the Korea government Ministry of Trade,Industry,and Energy(MOTIE)and the Korea Basic Science Institute(KBSI)National Research Facilities&Equipment Center(NFEC)(No.2019R 1A 6C 1010042)from the Ministry of Education of Korea.In addition,this work was partially supported by the N ano.M aterial Technology D evelopm ent Program(No.2009-0082580)Basic Science Research Program(No.2020R1C1C1007568)through the National Research Foundation of Korea funded by the Ministry of Science,Information&Communication Technology(ICT),and Future Planning.
文摘Core-shell hybrid nanomaterials have shown new properties and functions that are not attainable by their single counterparts.Nanoscale confinement effect by porous inorganic shells in the hybrid nanostructures plays an important role for chemical transformation of the core nanoparticles.However,metal-organic frameworks(MOFs)have been rarely applied for understanding mechanical insight into such nanoscale phenomena in confinement,although MOFs would provide a variety of properties for the confining environment than other inorganic shells such as silica and zeolite.Here,we examine chemical transformation of a gold nanorod core enclosed by a zeolitic imidazolate framework(ZIF)through chemical etching and regrowth,followed by quantitative analysis in the core dimension and curvature.We find the nanorod core shows template-effective behavior in its morphological transformation.In the etching event,the nanorod core is spherically carved from its tips.The regrowth on the spherically etched core inside the ZIF gives rise toformation of a raspberry-like branched nanostructure in contrast to the growth of an octahedral shape in bulk condition.We attribute the shell-directed regrowth to void space generated at the interfaces between the etched core and the ZIF shell,intercrystalline gaps in mult-domain ZIF shells,and local structural deformation from the acidic reaction conditions.
