Porous AlFm (OH) 3− m was prepared by heating AlF3· 3H2O. Methyl chlorodifluoroacetate was synthesized in 77% yield by the reaction of 1, 2-dichloro-1, 1, 2-trifluoro-2- methoxyethane with AlFm (OH) 3− m. The reaction mechanism was inferred in terms of surface property of AlFm (OH) 3− m.