The metal salt – Brønsted acidic ionic liquid system composed of ZnCl₂·1.74H₂O-1-(1-propylsulfonic)-3-methylimidazolium chloride can directly hydrolyze untreated cellulose in 78% total reducing sugar and 19% glucose yield at 37 °C, 1 atm in 4.0 days. The new chemical catalyst is used at a temperature lower than typical cellulase enzyme operating conditions.