Electron spin resonance studies of O-2(-) adsorbed on aluminophosphate molecular sieves

Abstract

Electron spin resonance (ESR) spectra of the superoxide ion, O-2(-), generated in dehydroxylated aluminophosphate (AlPO4) molecular sieves and related materials are presented. Among the molecular sieves studied here, the extra-large-pore VPI-5 shows the largest spin concentration of O-2(-), which corresponds to 2.9 x 10(18) ions per gram. Analysis of the g values of O-2(-) in AlPO4 molecular sieves reveals that the crystal field splittings, Delta, of the adsorbed O-2(-) are in the range of 1.32-1.60 eV and suggests that the crystal field interaction is dependent on the pore size of the molecular sieves.