CRYSTAL-STRUCTURE OF A NOVEL POROUS MEAPO PHASE - ZAPO-M1, (N(CH3)(4))(8)[ZN8AL24P32O128]

ZAPO-M1 was synthesized at 120 degrees C as an impurity among other zinco-aluminophosphates in the system P2O5-Al2O3-ZnO-tetrapropylammonium-tetramethylammonium-H2O. ZAPO-M1 is a microporous material with small pores formed by a two-dimensional pore system of 8-membered ring channels. ZAPO-M1 (structure type code: ZON) is characterized by a new host framework which is orthorhombic (space group Pbca) with a(0)=14.226(2) Angstrom, b(0)=15.117(2) Angstrom and c(0)=17.557(2) Angstrom and a unit cell composition of {N(CH3)(4)}(8)[Zn8Al24P32O128]. The single-crystal structure refinement using 1007 non-equivalent reflections led to a residual of R(W)=0.069. ZAPO-M1 has a framework structure that consists of only 4-, 6- and 8-membered rings of interconnected [TO4] tetrahedra. The structure contains eight symmetrically independent T positions and has a framework density of 16.6 T/1000 Angstrom(3). One half of the T positions are exclusively occupied by phosphorus atoms, the remaining four T positions contain aluminum as well as zinc atoms. The partial replacement of aluminum by zinc atoms gives the framework a negative charge which is compensated by tetramethylammonium cations. The (CH3N+ ions are located in 14-hedral [4(6)6(4)8(4)] cages (V approximate to 230 Angstrom(3)) which are formed by the intersection of the two 8-membered ring channels.