A sulfonic acid functionalized acidic ionic liquid modified silica catalyst was prepared in 68% overall yield from 3-chloropropyl silica by a simple two step method involving nucleophilic substitution of chlorine with imidazole, then condensation with 1,3-propanesultone and acidification using HCl. This silica supported acid catalyst was shown to be effective in the hydrolysis of cellulose (DP ∼ 450) dissolved in 1-n-butyl-3-methylimidazolium chloride at 70 °C, producing glucose and total reducing sugars in 26 and 67% yields respectively. © 2010 Elsevier Ltd. All rights reserved.