Tuning the atomic ordering of AFI framework with templates charge

Abstract

In this work, AlPO₄-5 (AFI) zeotype materials were synthesized using the microwave approach in the presence of two organic templates i.e. tripropylamine (R) and tetrapropylammonium (R⁺). The long- and short-range crystalline order of the samples were investigated by considering the effect of the template's charge on the atomic-level ordering of the AFI framework. Using advanced NMR spectroscopy, we shed the light on the importance of templates' role on the organization of the inorganic framework of aluminophosphates. The spectroscopic data clearly show a wider distribution of Al and P environments in the materials synthesized with the charged template (R⁺) due to the need of hydroxyl groups charge compensators that induce some bridges distortions. When a charged molecule (R⁺) was used, aluminum appears to be responsible for the charge compensation mechanism via the association of OH groups, impacting the environment of phosphorus as well. The hydroxyl groups needed for charge compensation in samples synthesized with R⁺ persist after calcination. Consequently, the hydrophilicity of the sample synthesized with R⁺ features approximatively two times higher values compared to the one synthesized with R.