ISOMORPHOUS ELEMENT SUBSTITUTION IN THE CHABAZITE-LIKE ALUMINOPHOSPHATE FRAMEWORK

Thermal investigations and Fenske-Hall SCF MO calculations have been u sed for studying isomorphous element substitution in the chabazite-lik e aluminophosphate framework prepared in the presence of tetraethylamm onium hydroxide as a template. The thermal measurements show that the temperature at which the template removal occurs increases as the elem ent varies in the Si-Zn-Mn-Co series. The Fenske-Hall SCF MO calculati ons on model segments of the framework indicate that the trend can be related to an appropriate decrease in basicity of the oxygen atom dire ctly bound to the element.