Catalytic activation of an unstrained, unactivated Si-C(sp(3)) bond in water to form methane and silanol by electrophilic rhodium(III) porphyrin [(por)R-III] in acidic aqueous solutions under visible light (lambda >= 420 nm) has been developed. Activation of the Si-C(sp(3)) bond occurs through direct Si-C bond cleavage, with methyl group transfer to rhodium to give a porphyrin rhodium methyl complex. Photolysis of (por)Rh-CH3 in water yields methyl radical and (por)Rh-II. Subsequently, (por)Rh-II reacts with water rapidly to produce (por)Rh-H and (por)Rh-OH. (por)Rh-OH is then protonated to regenerate (por)Rh-III-OH2, and (por)Rh-H undergoes hydrogen atom abstraction by methyl radical to form the observed methane.