SBE type cobalt-aluminophosphates (Co/Al ~ 1): synthesis aging effect, detemplation mechanism from coupled TGA/FTIR analyses, and structural stability after detemplation

Cobalt-rich SBE-type aluminophosphate (AlPO) microporous solids were prepared by employing different aging periods during the hydrothermal synthesis. According to XRD, SEM, and porosimetry tests, aging for 168 h results in a material with good long-range framework and textural features. The latter were analyzed after careful removal of the structure-directing agent (SDA) or detemplation, which produced a micropore surface area of ca. 600 m²/g, the highest ever reported for an AlPO having a multi-dimensional pore system and the highest cobalt-to-aluminum framework ratio. Coupled TGA/FTIR was employed in an attempt to elucidate the SDA decomposition mechanism in both inert and oxidative environments. Careful analysis confirmed that the latter case results in encapsulation of some of the detemplation species due to structural collapsing. Finally, the structural stability of detemplated material was evaluated in the presence of humidity and ambient air. The results indicate that the framework cobalt appear to readily oxidize upon adsorption of di-oxygen at ambient conditions, leading to an irreversible collapsing of the structure. However, the detemplated microporous solid appears to be stable in the presence of moist inert atmospheres.