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

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.

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► Acid treatment of NU-6(1) yields organic free layered precursor to NSI, MCM-39.
► MCM-39 is swollen by intercalation of polar organic compounds.
► Swelled and silica pillared MCM-39 has 2.5 nm galleries and high porosity.
► TEM reveals regular stacking of NSI layers in pillared MCM-39.
► Sub-NSI is calcined MCM-39 with shorter stacking height than zeolite NSI.