The AlPO 4 material UiO-12, [Al 3 P 3 O 12 (OH)] À [CH 3 NH 2 CH 3 ] , is obtained hydrothermally as a two-phase mixture with augelite and is isostructural with AlPO 4 -EN3 and some other AlPO 4 materials. The crystal structure of the assynthesized material, space group Pbca with a 13X57920(1) #
A, b 10X3511(2) # A and c 17X4655(4) # A, was solved from single crystal X-ray diraction data. The indicated decomposition of the tetramethylammonium template to dimethylammonium during synthesis was con®rmed by 13 C MAS-NMR data which, in addition, showed small amounts of methylammonium. The 31 P-MAS-NMR spectrum is consistent with three crystallographically non-equivalent Ppositions. UiO-12 undergoes complex structural rearrangements on heating, and has at 500°C transformed into a fully tetrahedral framework (UiO-12-500). The transformation involves the removal of encapsulated organic material and of bridging hydroxyl groups between ®ve-coordinated aluminum atoms. The structure of UiO-12-500, Al 3 P 3 O 12 , space group Pbca with a 13X9182 # A, b 9X6631 # A and c 18X0313 # A at 298 K, was re®ned from powder X-ray diraction data using a DLS optimized four-coordinated variant of UiO-12-as as starting model. The structure contains sheets of four-, six-and eight-membered rings linked via chains in a zigzag conformation.