Laponite-derived porous clay heterostructures: I. Synthesis and physicochemical characterization

Abstract

Porous clay heterostructures (PCHs) were obtained by a surfactant-directed assembly of Si precursor (tetraethylorthosilicate – TEOS) and Laponite clay. The materials were characterized with HRTEM, SEM, EDS, XRD, nitrogen adsorption/desorption at −196 °C, 29Si MAS NMR, and thermal analysis. Structural and textural studies revealed that molecular interactions leading to self-assembly in the Laponite/surfactants/TEOS system induce a break up of larger plate-like Laponite agglomerates, during which Laponite tactoids exfoliate into primary basic units and become randomly oriented. The silica network developed upon hydrolysis and thermal decomposition of TEOS contains both bulk Q 4 centres and surface Q 3 Si sites. Formation of porous silica linkage between the Laponite particles results in a change of the nitrogen isotherm character from IVb (Laponite) to IIb (PCHs) and leads to an increase of specific surface area, total pore volume and average pore diameter. Decrease of the clay:TEOS ratio results in PCH solids with a significantly higher specific surface area, but less resistant to treatment at elevated temperature.