We have developed a molecular simulation method for the generation of realistic atomic-level models for periodic mesoporous silicas. Using simplified interaction potentials and simplified representations of the templating micelles, the simulation follows the reaction path of the hydrothermal synthesis and calcination of the silica material in a kinetic Monte Carlo (kMC) simulation. The only input to the simulation is the geometry of the micelle and the number of silicic acid monomers at the beginning of the synthesis. We simulated the adsorption properties of the PMS models using Grand Canonical Monte Carlo simulation. With use of MCM-41 materials of different pore sizes as a prototype material, experimental and simulated adsorption isotherms for nitrogen, ethane, and carbon dioxide were compared, showing good agreement between simulation and experiment.