Synthesis and characterisation of aluminophosphate-based zeotype materials prepared with α,ω-bis(N-methylpyrrolidinium)alkane cations as structure-directing agents

Abstract

New routes to the preparation of two families of small pore microporous solids are described. Flexible diquaternary alkyl ammonium cations (C₄H₈)CH₃N⁺(CH₂)_nN⁺CH₃(C₂H₈), n = 3–5, have been found to act as structure directing agents in the synthesis of aluminophosphate-based materials of the ABC-6 group. The templates exhibit considerable selectivity in crystallising phases of the ERI or AFX-type (MeAPO-17 or MeAPO-56, respectively) from a wide variety of metalloaluminophosphate gels (Me = Mg²⁺, Co²⁺ or Si⁴⁺). For example, from gels containing Mg/P = 0–0.25, 1,4-bis(N-methylpyrrolidinium)butane cations gave MgAPO-17, and 1,5-bis(N-methylpyrrolidinium)pentane cations gave MgAPO-56. Notably, materials could be prepared with levels of metal-substitution tailored to a high degree and distributed non-randomly within the framework. As-prepared solids have been characterised by powder XRD, multinuclear solid state NMR, FT-IR, SEM, and thermal and elemental analysis.