Iron(III) chloride adsorbed on silica gel catalyzes the photodecomposition of dichloromethane under near-UV irradiation, functioning through photodissociation to produce chlorine atoms that initiate a radical chain. While the photocatalytic activity under these conditions is similar to that of FeCl4− heterogenized on an ion exchange resin, under solar irradiation the FeCl3/silica system is considerably more effective.