XPS studies of MCM 41 postmodified by a Schiff base copper complex

Abstract

Preliminary studies of the distribution of the copper complex in MCM 41 postmodified by a Schiff base (salen) copper complex have been carried out using x-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS). AAS showed 1.3 at% (atomic %) (0.65 mmolg- 1) of copper loading, which is in close agreement with 1.5 at% obtained from XPS analysis. Nitrogen sorption (77 K) shows a change from a Type IV to a Type I isotherm on postmodification, indicating a change in porosity of the material from mesoporous to microporous. This change in porosity corresponds to a reduction in surface surface area (from 813 m2g- 1 to 332 m2g- 1) and pore volume (from 0.39 cm3g- 1 to 0.02 cm3g- 1). The XPS argon ion etching results suggest that about a third of the copper complex is going inside the pores, thereby narrowing some pores and blocking others. The remaining copper complex goes on to the external surface of the material. This hypothesis is consistent with the observed changes detected by nitrogen sorption studies on postmodification of MCM 41.