Cooperative structure-directing effect in the synthesis of aluminophosphate molecular sieves in ionic liquids

Abstract

In situ two-dimensional NMR and fluorescence emission spectroscopy were employed to investigate the cooperative structure-direction effect of organic amine such as morpholine in the synthesis of aluminophosphate molecular sieves in ionic liquids. In situ rotating frame nuclear Overhauser effect spectra (ROESY) together with fluorescence measurements demonstrate that the aggregates between imidazolium cations and morpholines through intermolecular hydrogen bonds can be formed in the gel during the crystallization of molecular sieves. Combining with the characterizations of the solid products by solid-state NMR, it is verified that different aggregates of organic amines with imidazolium cations, which is similar to self-assembled supramolecular analogues, could act as the structure-directing agents for selective tuning of the framework topologies such as AEL, AFI and LTA in the final solid products.