Aluminophosphate Chain-to-Layer Transformation

The synthesis and characterization of two novel aluminophosphate materials, obtained from the same nonaqueous tetraethylene glycol−cyclopentylamine system, is reported. The first material, [Al 3 P 5 O 20 H] 5 - ·5[C 5 H 9 NH 3 + ], denoted UT-2, has a 1-D chain structure with a P:Al ratio of 5:3, rather than 1:1 as found in the aluminophosphate AlPO 4 -n molecular sieves. The UT-2 chains are hydrogen-bonded together by terminal phosphate groups and organized into a layered structure. The second material, [Al 2 P 3 O 12 H] 2 - ·2[C 5 H 9 NH 3 + ], denoted UT-3, has a 2-D layer structure with a P:Al ratio of 3:2. Both materials have bilayers of charge-balancing cyclopentylammonium cations interdisposed between anionic aluminophosphate sheets. Variable-temperature in situ PXRD establishes a clean solid-state structural transformation, at 200 °C, of UT-2 to UT-3. The discovery of this chain-to-layer conversion suggests a new paradigm for the templated assembly of 1-D chain, 2-D layer, and 3-D open-framework aluminophosphates.