Crystalline metal-organic frameworks (MOFs) are formed by reticular synthesis, which creates strong bonds between inorganic and organic units. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. The precision commonly exercised in their chemical modification and the ability to expand their metrics without changing the underlying topology have not been achieved with other solids. MOFs whose chemical composition and shape of building units can be multiply varied within a particular structure already exist and may lead to materials that offer a synergistic combination of properties.

The Chemistry and Applications of Metal-Organic Frameworks

Materials with good flexibility and high conductivity that can provide electromagnetic interference (EMI) shielding with minimal thickness are highly desirable, especially if they can be easily processed into films. Two-dimensional metal carbides and nitrides, known as MXenes, combine metallic conductivity and hydrophilic surfaces. Here, we demonstrate the potential of several MXenes and their polymer composites for EMI shielding. A 45-micrometer-thick Ti3C2Tx film exhibited EMI shielding effectiveness of 92 decibels (>50 decibels for a 2.5-micrometer film), which is the highest among synthetic materials of comparable thickness produced to date. This performance originates from the excellent electrical conductivity of Ti3C2Tx films (4600 Siemens per centimeter) and multiple internal reflections from Ti3C2Tx flakes in free-standing films. The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.

Electromagnetic interference shielding with 2D transition metal carbides (MXenes)

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

Complex Hydrides for Hydrogen Storage

New generation adsorbents for water treatment.

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.

http://science.sciencemag.org/content/sci/346/6215/1356.full.pdf

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

Recent decades have witnessed the explosive emergence of metal organic frameworks (MOFs) as functional ultrahigh surface area materials. Categorized as an intriguing class of hybrid materials, MOFs exhibit infinite crystalline lattices with inorganic vertices and molecular-scale organic linkers. Fortunately, the large internal surface areas and overall pore volumes, adjustable pore sizes, ultralow densities, and tunable framework–adsorbate interaction by ligand functionalization and metal choice, enable MOFs to be promising materials for wide applications. In particular, these remarkable properties render MOFs potential hydrogen storage materials. By virtue of their exceptionally high surface areas, unparalleled tenability and structural diversity, MOFs have become a hotspot of research within the scientific community. This paper reviews the different methods used for the synthesis of MOFs, the relationship between structural features and hydrogen adsorption, the strategies for hydrogen uptake improvement as well as the molecular simulation.

Hydrogen Storage in Metal-Organic Frameworks

Recent progress on study of hybrid hydrogels for water treatment

Recent research progress in the synthesis and properties of burning rate catalysts based on ferrocene-containing polymers and derivatives

In situ polymerization of aniline using ammonium peroxydisulphate (APS) as an oxidizing agent in the presence of chitosan (Cs) was used to synthesize Cs/polyaniline (PANI) nanofibers. The structure and morphology of the Cs/PANI nanofibers powder were characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–visible spectroscopy and scanning electron microscope (SEM). The surface of the Cs/PANI seems like interconnected nanofibers with diameters of approximately 50 nm. A film of the Cs/PANI nanofibers was built onto a quartz crystal microbalance (QCM) electrode by drop casting and this film was used to develop a sensor to measure the concentration of volatile organic vapors such as amines and alcohols in air. The frequency shifts (Δ f ) of the QCM, due to the vapor adsorption onto the Cs/PANI nanofibers film, were measured and related to the vapors’ concentrations. Linear relationships existed between the Δ f (Hz) and the analytes’ concentrations. The sensor showed a good sensitivity, reproducibility and reversibility. The influence of different temperatures on the vapor adsorption onto the Cs/PANI nanofibers film was studied. The kinetics of diffusion of the gases and the diffusion coefficients ( D ), were discussed.

Wael A. Amer

Papers

Hydrogen Storage in Metal-Organic Frameworks

Recent progress on study of hybrid hydrogels for water treatment

Recent research progress in the synthesis and properties of burning rate catalysts based on ferrocene-containing polymers and derivatives

Chitosan/polyaniline nanofibers coating on the quartz crystal microbalance electrode for gas sensing

Magnetic polyaniline-chitosan nanocomposite decorated with palladium nanoparticles for enhanced catalytic reduction of 4-nitrophenol