Zeolites and related crystalline microporous oxides-tetrahedrally coordinated atoms covalently linked into a porous framework-are of interest for applications ranging from catalysis to adsorption and ion-exchange. In some of these materials (such as zeolite rho) adsorbates, ion-exchange, and dehydration and cation relocation can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials, can be systematically contracted through dehydration at elevated temperatures to 'tune' the effective size of the pores giving access to the interior of the crystal. We show that this so-called 'molecular gate' effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2.

Magnetic zeolite composites with supported silver nanoparicles are a new class of multifunctional materials with potential applications as recyclable catalysts, disinfectants, and sorbents. This study evaluated the suitability of the magnetic composites as sorbents for the removal of elemental mercury vapor from flue gases of coal-fired power plants. The sorbents were found to completely capture mercury at temperatures up to 200 degrees C, and the mercury capacity of the sorbents was found to be affected by the state, content, and size of the silver particles in the composite. Cumulative or extended thermal treatments at 400 degrees C were found to improve the mercury capture capacity, allowing the sorbent to be regenerated and recycled multiple times without performance degradation. The magnetic sorbent was readily separated from fly ash by magnetic separation, leaving the fly ash essentially free of sorbent contamination. In initial in-plant tests, the sorbents were able to capture mercury from the flue gases of an operational, full-scale, coal-fired power plant The combination of mercury capacity, ease of separation and regeneration, and recyclability makes these multifunctional magnetic composites excellent candidate sorbentsforthe control of mercury emissions from coal-fired power plants.

The structure of strontium ion-exchanged ETS-4 titanosilicate has been refined from X-ray powder diffraction data and compared to the structure of sodium ETS-4. The framework of ETS-4 is highly faulted in two directions and can be described as an intergrowth of four polymorphs. Despite the faulting, both materials have open 8-ring channels in the b direction. Faulting probabilities in the a and c directions close to 50% allow the structures to be modeled using a superposition of the possible polymorphs for the purposes of Rietveld refinement. While the sodium ions in Na-ETS-4 are found to be distributed over two different cation sites, the ions in Sr-ETS-4 are found close to the same positions with the strontium ions selectively occupying the cation site coordinated to the chain-bridging titanium leaving unexchanged sodium ions in the 6-ring cation site. The chain-bridging titaniums in Sr-ETS-4 were found to be five-coordinated in square-pyramidal polyhedra, as indicated by an occupancy of the apical oxygen of 1.03 oxygens per unit cell and a Ti-O bond distance of 1.75 (0.04 Å to the apical oxygen. The ideal formula for Sr-ETS-4 was determined to be NaSr 4 Si 12 Ti 5 O 38 (OH)‚12H 2 O with lattice constants a ) 23.1962(12) Å, b ) 7.23810(33) Å, c ) 6.96517(31) Å, R ) β ) γ ) 90°in the Cmmm space group. Site ordering of the cations and the presence of five-coordinated titanium may help understanding the recently reported methane/nitrogen gas separation properties of this new molecular sieve.

A novel concept is proposed to synthesize a new class of composites featuring magnetic, molecular sieve and metallic nanoparticle properties. These multi‐functional materials have potential applications as recyclable catalysts, disinfectants and sorbents. The magnetic property enables effective separation of the spent composites from complex multiphase systems for regeneration and recycle, safe disposal of the waste and/or recovery of loaded valuable species. The zeolite molecular sieve provides a matrix which supports a remarkably new, simple, efficient and economical method to make stable, supported silver nanoparticles by silver ion exchange and controlled thermal reduction. The silver nanoparticles generated in this way have excellent properties such as high reactivity and good thermal stability without aggregation, which act as nano reactors for desired functionality in a wide range of applications. Magnetic component (Fe3O4), molecular sieve matrix (zeolite) and silver nanoparticles generated by ion exchange followed by controlled reduction, together form this unique novel composite with designed functions. It represents a practically operational, economical, sustainable and environmentally friendly new advanced functional material. This paper focuses on the novel synthesis and characterization of the composite, with an example of applications as sorbents for the removal of vapor‐phase mercury from the flue gas of coal‐fired power plants.

We report the hydrothermal synthesis of 10 µm × 100 µm × 10 µm single crystals of the microporous titanosilicate sodium-ETS-4. The crystallization of large needle-shaped Na-ETS-4 crystals is preceded by the formation and subsequent dissolution of the titanosilicate GTS-1. Large Na-ETS-4 crystals are obtained with purity higher than 97%. The structures of Na-ETS-4 and its Sr ion-exchanged form are solved from single-crystal X-ray diffraction data. It is suggested from the structure solution and further supported by the results of the empirical bond valence model that the bridging unit of ETS-4 contains five-coordinate titanium(IV). Infrared spectroscopy is also used to support the crystallographic results, with regard to the presence of charge-balancing protons and five-coordinate titanium. ETS-4 is, thus, one of only two synthetic titanosilicate materials containing five-coordinate titanium. We also discuss some structural differences between ETS-4 and its natural analogue, zorite.