Prevalence of the external surface over the internal pores in the spontaneous generation of tetrathiafulvalene radical cation incorporated in the novel delaminated ITQ-2 zeolite

Abstract

ITQ-2 is a novel delaminated zeolite whose crystalline sheets (2.5 nm depth) define a large external surface (∽720 m² g⁻¹) having 12-membered ring (MR) open cups together with a reduced microporosity due to a 10 MR channel system. This feature is the reverse of that of classical zeolites (i.e., much larger internal area compared to the external surface). Herein, we have used tetrathiafulvalene and triphenylamine to probe the capability of layered ITQ-2 zeolite to generate persistent organic radical cations compared to conventional Y, mordenite and ZSM-5 zeolites as well as to Al/MCM-41 (3.2 nm diameter) and amorphous silica–alumina. By selective silylation of the external cups, it has been found that formation of a significant concentration of persistent organic radical cations in ITQ-2 is a property that occurs within the open cups of the external surface rather than inside the 10 MR pores.