Combinatorial-topological modeling of the cluster self-assembly of zeolite crystal structures: computer search for molecular templates for new zeolite ISC-2

Abstract

The combinatorial-topological modeling of 3D periodic packings of layers composed of T₁₂ polyhedral clusters (t-hpr tiles in the form of hexagonal prisms) was carried out. The T12 clusters are among the most abundant units in the crystal structures of zeolites. The layers were produced by decoration of the vertices of the square and hexagonal (graphite-like) nets with T₁₂ clusters. All combinatorially possible patterns of 3D frameworks, which were constructed based on packings of decorated square nets, correspond to known zeolite structures: CHA (mineral chabazite, Ca₆(H₂O)₄₀Al₁₂Si₂₄O₇₂), AEI (AlPO-18, Al₂₄P₂₄O₉₆), SAV ((C₁₈H₄₂N₆)₂(H₂O)₇Mg₅Al₁₉P₂₄O₉₆), and KFI (Na₃₀(H₂O)₉₈Al₃₀Si₆₆O₁₉₂). The modeling using the same scheme and a decorated hexagonal net gave rise to the frameworks of three known zeolites, GME (gmelinite, (Ca,Na)₄(H₂O)₂₄A_l8Si₁₆O₄₈), AFX (SAPO-56, H₃Al₂₃Si₅P₂₀O₉₆), and AFT (AlPO-52, Al₃₆P₃₆O₁₄₄), as well as of one previously unknown hypothetical zeolite ISC-2 with the unit cell parameters a = 13.90 Å, c = 30.00 Å, V = 5019.7 ų, sp. gr. \(P\bar 6m2\). Zeolite ISC-2 contains a cavity with a new t-isc-2 topology [4²¹.6².8¹⁵], which is responsible for its unique framework. An analysis of the specially created database of topological types of molecules (TTM collection) containing geometric and topological characteristics of more than 300000 different molecules suggested an organic structure-directing agent, which stabilizes the t-isc-2 cavity and which can be used for the synthesis of ISC-2.