A range of iron and aluminum-containing mesoporous molecular sieves FeAlMCM-41 with different nsi/(n(Fe) + n(Al)) ratios have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. X-ray diffraction (XRD), N-2 adsorption, elementary analysis, UV-Vis, ESR and Al-27 MAS NMR spectroscopy. UV-Vis and ESR spectroscopy suggest that iron is present in tetrahedral coordination and imparts Bronsted acidity. The catalyst FeAlMCM-41 (n(Si)/n(Al) = 40; n(Si)/n(Fe) = 40) showed superior performance in the acid-catalyzed tert-butylation of phenol employing tert-butanol as the alkylation agent. At a reaction temperature of 200degreesC, a phenol conversion of 70.1% and a selectivity of ca. 75% for 4-tert-butylphenol (4-TBP) were observed. The catalyst FeAlMCM-41 (n(Si)/n(Me) = 50) shows a phenol conversion of 55.4% at a reaction temperature of 180degreesC, which is significantly higher as compared to AlMCM-41(56) and FeMCM-41(50). Over these catalysts, phenol conversions amounted to 35.9 and 21.1%, respectively. (C) 2004 Elsevier B.V. All rights reserved.