Cyclopentanone is a promising building block in the conversion of biomass to fuels. It can be readily obtained from furanics derived from biomass and can be converted to intermediate products in the molecular weight range compatible with fuels via C-C bond forming reactions. Among them, aldol condensation is a promising route. Conventional MgO catalysts are intrinsically active to catalyze this reaction, but they usually exhibit low surface areas and low stability in the presence of liquid water. The nitrate-citrate combustion method results in high surface area oxides with high condensation activity, but they are still susceptible to water attack. Here, we show that hydrophobic MgO-based catalysts functionalized with octadecyltrichlorosilane (OTS) exhibit remarkable stability in the liquid phase under conditions in which a conventional MgO deactivates in short time.