Modelling the adsorption of small molecule gases such as N2 , CH4 and CO2 in porous solids can provide valuable insights for the development of next generation materials. Employing a grand canonical Monte Carlo simulation code developed in our group, the adsorption isotherms of CH4 and CO2 in many metal organic frameworks have been calculated and compared with experimental results. The isotherms computed within a force field approach are able to well reproduce the experimental data. Key functional groups in the solids which interact with gas molecules and the nature of their interactions have been identified. The most favorable interaction sites for CH4 and CO2 in the framework solids are located in the linkers which are directed towards the pores. The structure of a perfluorinated conjugated microporous polymer has been modelled and it is predicted to take up 10% more CO2 than its hydrogenated counterpart. In addition, the vibrational, orientational and diffusive properties of CO2 adsorbed in the solids have been examined using molecular dynamics simulations. Intermolecular modes of such adsorbed species exhibit a blue shift with increasing gas pressure.