On the thermal behaviour of the crystalline hybrid organic-inorganic aluminosilicate ECS-3

The thermal behaviour of the crystalline hybrid organic-inorganic aluminosilicate ECS-3 was studied by in situ X-ray diffraction, thermal analysis, nitrogen adsorption and NMR spectroscopy. In situ X-ray diffraction demonstrated that ECS-3 is thermally stable up to 150 degrees C where a significant fraction of water molecules (37%) are still retained inside the pores. After heating at 200 degrees C in air, X-ray-diffraction data evidenced structural collapse, nitrogen adsorption was drastically reduced and C-13 and Si-29 MAS NMR studies confirmed single-sided Si-C bond rupture. Collective observations indicate thatnearly 20% of the phenylene bridges were converted to phenyl groups while a corresponding amount of silicon T sites became Q. Structural collapse did not occur at 200 degrees C under vacuum conditions, supporting a mechanism where water promotes Si-C cleavage by initiating proton transfer to the phenylene. (C) 2013 Elsevier Inc. All rights reserved.