STABILITY OF THE Co(II) VALENCE STATE IN ALUMiNOPHOSPHATE-5 MOLECULAR SIEVE TO CALCINATION FROM LOW TEMPERATURE ELECTRON SPIN RESONANCE

摘要

As-synthesized CoAPO-5 is blue and it becomes yellow-green after calcination in oxygen. This was interpreted by several research groups as indicating a valence state change from Co(II) to Co(ni); however, our electron spin resonance and temperature programmed desorption results provide no evidence for Co(IlI) and are consistent with all the framework species existing as Co(II) both before and after calcination.