Shaozhou Li

Imparting functionality to a metal–organic framework material by controlled nanoparticle encapsulation

Microporous metal-organic frameworks (MOFs) that display permanent porosity show great promise for a myriad of purposes. The potential applications of MOFs can be developed further and extended by encapsulating various functional species (for example, nanoparticles) within the frameworks. However, despite increasing numbers of reports of nanoparticle/MOF composites, simultaneously to control the size, composition, dispersed nature, spatial distribution and confinement of the incorporated nanoparticles within MOF matrices remains a significant challenge. Here, we report a controlled encapsulation strategy that enables surfactant-capped nanostructured objects of various sizes, shapes and compositions to be enshrouded by a zeolitic imidazolate framework (ZIF-8). The incorporated nanoparticles are well dispersed and fully confined within the ZIF-8 crystals. This strategy also allows the controlled incorporation of multiple nanoparticles within each ZIF-8 crystallite. The as-prepared nanoparticle/ZIF-8 composites exhibit active (catalytic, magnetic and optical) properties that derive from the nanoparticles as well as molecular sieving and orientation effects that originate from the framework material.

Synthesis of hexagonal close-packed gold nanostructures

Solid gold is usually most stable as a face-centred cubic (fcc) structure. To date, no one has synthesized a colloidal form of Au that is exclusively hexagonal close-packed (hcp) and stable under ambient conditions. Here we report the first in situ synthesis of dispersible hcp Au square sheets on graphene oxide sheets, which exhibit an edge length of 200-500 nm and a thickness of ~ 2.4 nm (~ 16 Au atomic layers). Interestingly, the Au square sheet transforms from hcp to a fcc structure on exposure to an electron beam during transmission electron microscopy analysis. In addition, as the square sheet grows thicker (from ~ 2.4 to 6 nm), fcc segments begin to appear. A detailed experimental analysis of these structures shows that for structures with ultrasmall dimensions (for example, <~ 6 nm thickness for the square sheets), the previously unobserved pure hcp structure becomes stable and isolable.

A Family of Metal‐Organic Frameworks Exhibiting Size‐Selective Catalysis with Encapsulated Noble‐Metal Nanoparticles

The encapsulation of noble-metal nanoparticles (NPs) in metal-organic frameworks (MOFs) with carboxylic acid ligands, the most extensive branch of the MOF family, gives NP/MOF composites that exhibit excellent shape-selective catalytic performance in olefin hydrogenation, aqueous reaction in the reduction of 4-nitrophenol, and faster molecular diffusion in CO oxidation. The strategy of using functionalized cavities of MOFs as hosts for different metal NPs looks promising for the development of high-performance heterogeneous catalysts.

Graphene Oxide‐Templated Synthesis of Ultrathin or Tadpole‐Shaped Au Nanowires with Alternating hcp and fcc Domains

Ultrathin Au nanowires (AuNWs) and tadpole-shaped nanowires are synthesized on graphene oxide (GO) sheet templates. For the first time, 1.6 nm-diameter AuNWs are shown to contain hexagonal close-packed (hcp) crystal domains, and the tadpole-shaped nanowires exhibit alternating sets of hcp and face-centered cubic (fcc) structures, associated with variation in wire thickness.

Mesoporous Metal–Organic Frameworks with Size‐, Shape‐, and Space‐Distribution‐Controlled Pore Structure

W. Zhang, Z. Xu, Prof. W. Huang, Prof. F. Huo Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM) Jiangsu National Synergistic Innovation Center for Advanced Materials (SICAM) Nanjing Tech University (NanjingTech) 30 South Puzhu Road Nanjing 211816 , PR China W. Zhang, Y. Liu, Prof. G. Lu, Prof. S. Li, C. Cui, J. Wu, Prof. F. Huo School of Materials Science and Engineering Nanyang Technological University 50 Nanyang Avenue Singapore 639798 , Singapore E-mail: fwhuo@ntu.edu.sg Prof. Y. Yang School of Chemical and Biomedical Engineering Nanyang Technological University 62 Nanyang Drive Singapore 637459 , Singapore Dr. Y. Wang, Prof. H. Chen Division of Chemistry and Biological Chemistry Nanyang Technological University 21 Nanyang Link Singapore 637371 , Singapore Z. Xu, Prof. D. Tian College of Science Nanjing Tech University (NanjingTech) Puzhu Road Nanjing 211816 , PR China J. S. DuChene, Prof. W. D. Wei Department of Chemistry and Center for Nanostructured Electronic Materials University of Florida Gainesville , FL 32611 , USA

Photochemically Controlled Synthesis of Anisotropic Au Nanostructures: Platelet-like Au Nanorods and Six-Star Au Nanoparticles

We report the shape-controlled synthesis of anisotropic Au nanostructures through TiO(2)-assisted photochemical reduction of HAuCl(4). By using this method, we have successfully synthesized the platelet-like Au nanorods and six-star Au nanoparticles. Importantly, the platelet Au nanorod exhibits the unique asymmetric five-twinned structure. The colloidal TiO(2) sols were used as both the photocatalyst to initiate the reaction and the stabilizing agent for the produced Au nanostructures. Significantly, in this photochemical process, the tunable irradiation intensity allows us to kinetically control the crystal evolution at various growth stages, leading to the shape difference of ultimate gold nanostructures. Our synthetic method shows a great potential as an alternative or supplement to the other wet chemical approaches for the shape-control of metallic nanostructures.

Interdiffusion Reaction-Assisted Hybridization of Two-Dimensional Metal–Organic Frameworks and Ti3C2Tx Nanosheets for Electrocatalytic Oxygen Evolution

Two-dimensional (2D) metal-organic framework (MOF) nanosheets have been recently regarded as the model electrocatalysts due to their porous structure, fast mass and ion transfer through the thickness, and large portion of exposed active metal centers. Combining them with electrically conductive 2D nanosheets is anticipated to achieve further improved performance in electrocatalysis. In this work, we in situ hybridized 2D cobalt 1,4-benzenedicarboxylate (CoBDC) with Ti3C2Tx (the MXene phase) nanosheets via an interdiffusion reaction-assisted process. The resulting hybrid material was applied in the oxygen evolution reaction and achieved a current density of 10 mA cm-2 at a potential of 1.64 V vs reversible hydrogen electrode and a Tafel slope of 48.2 mV dec-1 in 0.1 M KOH. These results outperform those obtained by the standard IrO2-based catalyst and are comparable with or even better than those achieved by the previously reported state-of-the-art transition-metal-based catalysts. While the CoBDC layer provided the highly porous structure and large active surface area, the electrically conductive and hydrophilic Ti3C2Tx nanosheets enabled the rapid charge and ion transfer across the well-defined Ti3C2Tx-CoBDC interface and facilitated the access of aqueous electrolyte to the catalytically active CoBDC surfaces. The hybrid nanosheets were further fabricated into an air cathode for a rechargeable zinc-air battery, which was successfully used to power a light-emitting diode. We believe that the in situ hybridization of MXenes and 2D MOFs with interface control will provide more opportunities for their use in energy-based applications.

Self‐Assembled Metal‐Organic Frameworks Crystals for Chemical Vapor Sensing

A 3D metal-organic frameworks (MOFs) crystals film is obtained via Langmuir-Blodgett technique and used as a photonic sensor for chemical vapor detection. The MOFs crystals film exhibits both acute responses towards various chemical vapors and high controllability in terms of peak intensity and position. The method represents a general, facile and flexible strategy for the fabrication of MOFs-based photonic sensors.

Unconventional Nucleation and Oriented Growth of ZIF‐8 Crystals on Non‐Polar Surface

Zeolitic imidazolate framework-8 (ZIF-8) crystals show unconventionally selective nucleation and oriented growth on a patterned self-assembled monolayer (SAM) surface. The growth selectivity and crystal orientation are also affected by the odd-even effect for SAMs. The oriented growth of the ZIF-8 crystals is found to result from fast crystallization of the nuclei triggered by the specific SAM surfaces.

Controlled incorporation of nanoparticles in metal-organic framework hybrid thin films.

A facile encapsulation strategy was reported for preparing nanoparticles/metal-organic framework hybrid thin films which exhibit both the active (catalytic, magnetic, and optical) properties derived from the NPs and the size-selectivity originating from the well-defined microporous structure of the MOF thin films.