Four heteropolyhedral microporous silicates A3REESi6O152.25H2O crystallizing in the Cmm2 space group and based on 41516182 tetrahedral sheets (A3 = Na2.74K0.26, REE = Ce, abbreviated as TR05; TR06: A3 = Na2.72K0.28, REE = La; TR07: A3 = Na3, REE = La; TR08: A3 = Na2.74(H3O)0.26, REE = La0.68Eu0.32) have been hydrothermally synthesized in Teflon-lined autoclaves at 503 K and structurally characterized using X-ray diffraction single-crystal data (Oxford Gemini R Ultra diffractometer equipped with a CCD area detector, MoKα radiation). The crystal structures were solved by direct methods and refined to R = 0.033 [TR05; 2987 reflections with Io > 2σ(Io)], R = 0.077 [TR06; 3022 reflections with Io > 2σ(Io)], R = 0.053 [TR07; 1896 reflections with Io > 2σ(Io)] and R = 0.051 [TR08; 2877 reflections with Io > 2σ(Io)]. Except for TR05, diffraction data have been collected on {001} twins by merohedry. The four structures are isotypic and based on strongly corrugated 41516182 silicate sheets interconnected along [010] by seven-coordinated REE polyhedra to form a microporous heteropolyhedral framework. The framework is crossed by three systems of ellipsoidal channels that host H2O molecules and alkaline atoms. The channels run either parallel or perpendicular to the silicate sheets; the largest effective channel width is 4.7x2 Å. In TR08 some (H3O)+ replaces alkalis. Although the H atoms have not been localized, the configuration of the hydrogen bonding has been deduced from bond lengths and angles.
New RE microporous heteropolyhedral silicates containing 41516182 tetrahedral sheets
CADONI, MARCELLA;FERRARIS, Giovanni
2010-01-01
Abstract
Four heteropolyhedral microporous silicates A3REESi6O152.25H2O crystallizing in the Cmm2 space group and based on 41516182 tetrahedral sheets (A3 = Na2.74K0.26, REE = Ce, abbreviated as TR05; TR06: A3 = Na2.72K0.28, REE = La; TR07: A3 = Na3, REE = La; TR08: A3 = Na2.74(H3O)0.26, REE = La0.68Eu0.32) have been hydrothermally synthesized in Teflon-lined autoclaves at 503 K and structurally characterized using X-ray diffraction single-crystal data (Oxford Gemini R Ultra diffractometer equipped with a CCD area detector, MoKα radiation). The crystal structures were solved by direct methods and refined to R = 0.033 [TR05; 2987 reflections with Io > 2σ(Io)], R = 0.077 [TR06; 3022 reflections with Io > 2σ(Io)], R = 0.053 [TR07; 1896 reflections with Io > 2σ(Io)] and R = 0.051 [TR08; 2877 reflections with Io > 2σ(Io)]. Except for TR05, diffraction data have been collected on {001} twins by merohedry. The four structures are isotypic and based on strongly corrugated 41516182 silicate sheets interconnected along [010] by seven-coordinated REE polyhedra to form a microporous heteropolyhedral framework. The framework is crossed by three systems of ellipsoidal channels that host H2O molecules and alkaline atoms. The channels run either parallel or perpendicular to the silicate sheets; the largest effective channel width is 4.7x2 Å. In TR08 some (H3O)+ replaces alkalis. Although the H atoms have not been localized, the configuration of the hydrogen bonding has been deduced from bond lengths and angles.
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