Chemisorption of chromium acetylacetonate on porous high surface area silica

• Published in: Applied surface science 1994-01, Vol.75 (1), p.220-227
• Main Authors: Haukka, Suvi, Lakomaa, Eeva-Liisa, Suntola, Tuomo
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-gas interface; Surface physical chemistry
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/0169-4332(94)90162-7

Atomic layer epitaxy (ALE) reactions (i.e. saturating gas-solid reactions) of chromium acetylacetonate (Cr(acac) 3) at 200–280°C with silica preheated at 200–820°C were studied by determining chromium and carbon concentrations, recording FTIR spectra, and reacting Cr(acac) 3 with the silylated silica surface. Cr(acac) 3 was found to be selectively chemisorbed to silica through reaction with the isolated OH groups, leading to release of one acac ligand. The relatively large size of the supported chromium complex that formed had a highly controlling effect on the amount of chromium atoms bound. In addition to this steric hindrance, the saturation density of chromium could be further regulated by the preheat temperature of the silica, which determines the number of OH groups, and by the reaction temperature. The reaction with the silylated silica surface provided a means for achieving an even lower saturation density of chromium and confirmed that the strongly H-bonded OH groups present on silica preheated at 200°C were only partly reactive. The ligands of the surface complex could be removed by water vapor and air treatment.