Xinlei Liu

Metal-organic framework nanosheets as building blocks for molecular sieving membranes

Layered metal-organic frameworks would be a diverse source of crystalline sheets with nanometer thickness for molecular sieving if they could be exfoliated, but there is a challenge in retaining the morphological and structural integrity. We report the preparation of 1-nanometer-thick sheets with large lateral area and high crystallinity from layered MOFs. They are used as building blocks for ultrathin molecular sieve membranes, which achieve hydrogen gas (H2) permeance of up to several thousand gas permeation units (GPUs) with H2/CO2 selectivity greater than 200. We found an unusual proportional relationship between H2 permeance and H2 selectivity for the membranes, and achieved a simultaneous increase in both permeance and selectivity by suppressing lamellar stacking of the nanosheets. Crystalline sheets exfoliated from layered metal-organic framework materials are formed into selective membranes. Metal-organic framework material membranes There continues to be a lot of interest in developing membranes for gas separations that go beyond the current polymer membranes used commercially for this purpose. Peng et al. took a porous metal-organic framework material with a layered structure and exfoliated it to give nanometer-thick molecular sieves. The membranes were exceptionally good at separating hydrogen gas from carbon dioxide both in terms of permeance and selectivity. Science, this issue p. 1356

An Organophilic Pervaporation Membrane Derived from Metal–Organic Framework Nanoparticles for Efficient Recovery of Bio-Alcohols†

adsorption of water before the onset of capillary condensation. [12] All the above-mentioned characteristics suggest that ZIF-8 nanoparticles could be used as fillers in mixed-matrix membranes (MMMs) for the recovery of organic compounds from aqueous solutions by adopting organophilic pervaporation (OPV) technology. Pervaporation is a membrane process based on a sorption–diffusion mechanism, and is considered the most promising technology for molecular-scale liquid/ liquid separations. [13] Herein we show that both pervaporation

Strain-Induced Ultrahard and Ultrastable Nanolaminated Structure in Nickel

Taking the Strain When heavily deformed through compressive or torsional loading, crystalline metals will generate an increasing density of defects or dislocations that effectively strengthens the metal against further deformation. However, at some stage, the fine-grained structure that forms saturates. Liu et al. (p. 337; see the Perspective by Ramtani), show that combining the application of a very-high-rate shear deformation with high strain gradients to the surface layer of a pure sample of nickel can overcome this saturation. Instead of a three-dimensional fine-grained structure, a top layer with a two-dimensional layered structure occupied the first 80 micrometers. In addition to being stronger, this layered nickel structure was also more thermally stable. Heavy shearing can produce a stronger, more thermally robust nickel microstructure. [Also see Perspective by Ramtani] Heavy plastic deformation may refine grains of metals and make them very strong. But the strain-induced refinement saturates at large strains, forming three-dimensional ultrafine-grained (3D UFG) structures with random orientations. Further refinement of this microstructure is limited because of the enhanced mobility of grain boundaries. Very-high-rate shear deformation with high strain gradients was applied in the top surface layer of bulk nickel, where a 2D nanometer-scale laminated structure was induced. The strongly textured nanolaminated structure (average lamellar thickness of 20 nanometers) with low-angle boundaries among the lamellae is ultrahard and ultrastable: It exhibits a hardness of 6.4 gigapascal—which is higher than any reported hardness of the UFG nickel—and a coarsening temperature of 40 kelvin above that in UFG nickel.

Highly Water-Stable Zirconium Metal–Organic Framework UiO-66 Membranes Supported on Alumina Hollow Fibers for Desalination

In this study, continuous zirconium(IV)-based metal-organic framework (Zr-MOF) membranes were prepared. The pure-phase Zr-MOF (i.e., UiO-66) polycrystalline membranes were fabricated on alumina hollow fibers using an in situ solvothermal synthesis method. Single-gas permeation and ion rejection tests were carried out to confirm membrane integrity and functionality. The membrane exhibited excellent multivalent ion rejection (e.g., 86.3% for Ca(2+), 98.0% for Mg(2+), and 99.3% for Al(3+)) on the basis of size exclusion with moderate permeance (0.14 L m(-2) h(-1) bar(-1)) and good permeability (0.28 L m(-2) h(-1) bar(-1) μm). Benefiting from the exceptional chemical stability of the UiO-66 material, no degradation of membrane performance was observed for various tests up to 170 h toward a wide range of saline solutions. The high separation performance combined with its outstanding water stability suggests the developed UiO-66 membrane as a promising candidate for water desalination.

Improvement of hydrothermal stability of zeolitic imidazolate frameworks

The metal-organic framework ZIF-8, which undergoes hydrolysis under hydrothermal conditions, is endowed with high water-resistance after a shell-ligand-exchange-reaction. The stabilized ZIF-8 retains its structural characteristics with improved application performances in adsorption and membrane separation.

A review of tele-immersive applications in the CAVE research network

This paper presents an overview of the tele-immersion applications that have been built by collaborators around the world using the CAVERNsoft toolkit, and the lessons learned from building these applications. In particular the lessons learned are presented as a set of rules-of-thumb for developing tele-immersive applications in general.

ERP research, development and implementation in China: an overview

An Enterprise Resource Planning (ERP) system is a highly integrated enterprise information system that manages all aspects of the business operations of an enterprise including production planning, purchasing, engineering design, manufacturing, marketing, distribution, accounting and customer service. In the last two decades, Manufacturing Resource Planning (MRP) and ERP have been successfully introduced into Chinese industry. Supported by sponsored research programmes, the research outcomes on ERP systems by Chinese academic researchers have been directly supporting the Chinese ERP software industry. An overview of ERP research and its development and implementation in China will be given here. The research trend of ERP systems will also be discussed.

Metal‐Substituted Zeolitic Imidazolate Framework ZIF‐108: Gas‐Sorption and Membrane‐Separation Properties

A series of dual-metal zeolitic imidazolate framework (ZIF) crystals with SOD and RHO topologies was synthesised by metal substitution from ZIF-108 (Zn(2-nitroimidazolate)2 , SOD topology) as the parent material. This was based on the concept that metal substitution of ZIF-108 requires a much lower activation energy than homogenous nucleation owing to the metastability of ZIF-108. In-depth investigations of the formation processes of the daughter ZIFs indicated that the transformation of ZIF-108 is a dissolution/heterogeneous nucleation process. Typical isostructural Co(2+) substitution mainly occurs at the outer surface of ZIF-108 and results in a core-shell structure. On the contrary, the Cu(2+) -substituted ZIF has a RHO topology with a homogeneous distribution of Cu(2+) ions in the structure. Substitution with Ni(2+) resulted in a remarkable enhancement in adsorption selectivity toward CO(2) over N(2) by a factor of up to 227. With Co(2+) -substituted nanoparticles as inorganic filler, a mixed matrix membrane based on polysulfone displayed greatly improved performance in the separation of H(2)/CH(4), CO(2)/N(2) and CO(2)/CH(4).