We present first-principles (based on electronic structure calculations) molecular dynamics simulations of the adsorption of methanol and water in zeolites. in contrast to most previous calculations we take the infinite zeolite structure fully into account. Our calculations reproduce the measured IR spectra, and thus allow for the first time a direct assignment of the measured bands. Methanol and water appear not to be protonated at low (one molecule per acid site) coverages. At higher coverages, however, the proton detaches from the framework and is available for acid catalyzed reactions in the zeolite. We precede our discussion with a critical evaluation of available theoretical approaches.