Intercalation chemistry of NU-6(1), the layered precursor to zeolite NSI, leading to the pillared zeolite MCM-39(Si)

Abstract

The layered material NU-6(1), precursor to zeolite NSI, contains 4,4′-dipyridyl (dipy) structure directing agent between layers composed of silica. The intercalated dipy has been removed by treatment with 2 M acid solution producing organic-free lamellar product, MCM-39. It has considerably shorter unit cell in the layer stacking direction of approximately 1.7 nm compared to 2.7 nm in NU-6(1). MCM-39 can be re-intercalated with various amines with expansion of the interlamellar space. Especially important is the treatment with hexadecyltrimethylammonium hydroxide, which affords swollen NSI and enables conversion into the pillared derivative, MCM-39(Si), with permanently expanded interlayer separation and enhanced porosity. The crystallographic repeat in MCM-39(Si) is equal to ca. 3.7 nm while TEM shows extensive, uniform, multilayer pillared zeolite structure. Calcination of MCM-39 without intercalated organic compound produces material with stacking dimension (unit cell) shorter than in the zeolite NSI. It is attributed to non-congruent condensation and the product is denoted as Sub-NSI.