(C4N2H12)3·H2O][(Al2P3O12)2]: A new anionic open-framework aluminophosphate with helical chains and multi-directional intersecting twelve-ring channels

Abstract

Abstract A new three-dimensional (3D) anionic interrupted open-framework aluminophosphate [(C4N2H12)3·H2O][(Al2P3O12)2] (denoted AlPO-JU88) with an Al/P ratio of 2/3 was hydrothermally synthesized by using piperazine as a structure directing agent. The structure was determined by single-crystal X-ray diffraction structural analysis and was further characterized by X-ray powder diffraction, elemental (CHN), thermogravimetric (TG), and NMR analyses. The strict alternation of Al-centered tetrahedra (AlO4) and P-centered tetrahedra (PO2( O)2 and PO3( O)) via bridging oxygen atoms resulted in a 3D open-framework featuring a new type of super-cage of 46128. Six racemic helical (31 or 32) chains were linked together to form a twelve-ring (12R) channel along the [0 0 1] direction, forming a multi-directional intersecting 12R channel system together with the 12R channels run along [2 4 1], [2 –2 1], and [− 4 − 2 1] directions. The negative charge of the framework was balanced by doubly protonated piperazine molecules. Ion exchange experiment suggested that 22 mol% of the protonated piperazine can be exchanged by Na cations, showing a better ion exchange property for the 3D interrupted open-framework aluminophosphates.