Hydrothermal synthesis and characterization of two ammonium-templated cobalt aluminophosphates

Abstract

Two new cobalt-substituted aluminophosphates (CoAPOs) with ammonium cation-templates, (NH ₄ ) ₂ [(OH) _0.95 (H ₂ O) _0.05 ] ₂ [Co _0.05 Al _0.95 ] ₂ (PO ₄ ) ₂ and (NH ₄ )[(OH) _0.95 (H ₂ O) _0.05 ][Co _0.025 Al _0.975 ] ₂ ·2H ₂ O, have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, thermogravimetry, elemental analysis, mass spectrometry and IR spectroscopy. The first compound crystallizes in a new zeolite-like structure type where Co ²⁺ substitutes for Al ³⁺ at both trigonal bipyramidal and octahedral sites. The second CoAPO is isostructural with a known aluminophosphate, AlPO-15, where all metal sites are octahedrally coordinated. The channels in both compounds are occupied by the charge-balancing NH ₄ ⁺ -templates. The compounds are stable up to ca. 350 °C above which temperature they become amorphous.