日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Recently, we successfully synthesized novel high-silica zeolite CDS-1 by topotactic conversion from a new three-dimensional layered silicate PLS-1. PLS-1 is obtained by hydrothermal synthesis with SiO₂-KOH-tetramethylammonium hydroxide-1,4-dioxane-H₂O system. Crystal structure of PLS-1 was determined by ab-initio technique using conventional X-ray powder diffraction data. Crystal system, lattice parameters and chemical composition of PLS-1 are monoclinic phase with space group of P2₁/m and of a=10.5710(5) Å, b=14.0064(3) Å, c=7.4220(2) Å, β=98.014(4)゜ and Si₁₈O₃₄(OH)₄K_1.3·1.7{(CH₃)₄NOH}, respectively. Framework of PLS-1 composed of all 5-MR is consistent with a part of ferrierite framework. We estimated that new zeolite CDS-1 could be formed by a topotactic dehydration-condensation between the layers of a new silicate with a layer structure consisting of face sharing of pentagonal cylinders, and so available microporous concisting of face sharing of pentagonal cylinders, and so available microporous stractures structures were simulated and designed by a molecular dynamics calculation. Experimentally, CDS-1 could be obtained by complete block dehydration-condensation of PLS-1 powder under evacuated conditions. Crystal structure of CDS-1 was determined by the Rietveld refinement based on simulated models. Space group and lattice constants were Pnma and a=18.355(3) Å, b=13.779(2) Å and c=7.3674(6) Å, respectively. CDS-1 has a novel topology with two 8-MR straight channels between pentagonal-cylinder layered blocks. Here, the novel high-silica zeolite CDS-1 (type CDO) is reviewed.