Structural models and physical properties of several amorphous microporous polymers (AMPs) have been investigated using molecular dynamics simulations in an all-atom framework. The modeled structures of AMPs are quantitatively consistent with experimental observations. A linear relationship between the accessible surface area (ASA) and mass density of AMPs has been established. In the AMP network constituted by planar nodes, near-neighbor nodes are oriented parallel to each other. The microporous structural models are further validated by the calculation of CO2 and N2 adsorption isotherms at 298 and 77 K, respectively, obtained through Grand Canonical Monte Carlo (GCMC) simulations. The isotherms and isosteric heat of adsorption computed within a force field approach are able to well reproduce the experimental results. The nature of interactions between the functional groups of the AMPs framework and CO2 have been identified. An excellent CO2 uptake with high heat of adsorption has been observed in AMPs containing nitrogen-rich building blocks.