Among the furan-based compounds, furfural (FUR) shows interesting properties as building-block or industrial solvent. It is produced from pentosan-rich biomass via xylose cyclodehydration. The current FUR production uses homogeneous catalysts and steam. According to recent studies, the reaction mechanism is different in the presence of Lewis (L) or Bronsted (B) sites. In this work, partially hydroxylated MgF2 catalysts, containing bifunctional Lewis and Bronsted properties, were further functionalized using different fluorosulfonic precursors. Its main objective was to test these solids as catalysts for xylose conversion to furfural. Extensive characterization techniques using TG-MS, F-19-MAS-NMR, or pyridine adsorption confirmed the substitution of surface OH groups by stronger Bronsted sites. The activity data showed a considerable change of the reaction kinetics and a final furfural selectivity of 90% at 160 degrees C in water/toluene for optimized LIB ratios by the one-step grafting technique. Moreover, the reaction analyses and the change of conversion pathways were studied. (C) 2013 Elsevier Inc. All rights reserved.