Incorporation of transition metal ions into MeAPO/MeAPSO molecular sieves

The synthetic incorporation of transition metal ions into aluminophosphate and silicoaluminophosphate molecular sieve frameworks is studied by electro n spin-echo modulation (ESEM) spectroscopy. Based mainly on bulk chemical c omposition of the product, it has been suggested that divalent and trivalen t metal ions such as Mn(II), Co(II), Cr(III). and Fe(III) substitute for fr amework aluminum sites. On the basis of P-31 ESEM results, we originally su ggested a framework phosphorus site for the incorporation of metal ions suc h as Ni(II) and Cr(III) in NiAPSQ-5 and CrAPSO-5 molecular sieves. This sit e was later supported for other metal ions such as TI(IV), V(IV), and Cu(II ), In this work, we have extended such studies to Mn(II) and Fe(III) to bet ter understand the metal substitution sites in AlPO4 frameworks. Irrespecti ve of the particular metal ion, the P-31 ESEM spectra of MeAPO/MeAPSO molec ular sieves can be interpreted best on the basis of metal incorporation at a framework phosphorus site, Strong Al-27 modulations are also observed for these materials, which supports the P-31 ESEM result that incorporated met al ions are located nearer to aluminum than phosphorus.