Synthesis of porous clay heterostructures from high charge mica-type aluminosilicates

Abstract

High charge micas are ideal materials to be used as porous solid acids because of their extraordinarily high content of framework aluminium atoms and their thermal stability. However, all efforts to create porosity in these materials have led to a disordered porous structure, since the full process is compromised by the highly layer attractive forces and hence by the incorporation stage of the porous wall precursors between the clay layers. Thermally stable and ordered mesoporous materials were synthesized for the first time from those swelling brittle micas through a surfactant templating approach. The interlayer space was firstly pre-expanded using alkylammonium cations, giving rise to a homogeneous organic–inorganic hybrid structure, which directs the polymerization step of the silica source. A regular porous structure in the supermicropore to the small mesopore range (15–25 Å) together with an exclusive acidity was found after sample calcination. The extraordinary content of framework aluminium is responsible for the large number of acid sites, both in the rare medium and strongly acidic regions. The thermal stability of the new synthesised materials was also tested.