Absorption in amine solutions and adsorption on supported amine adsorbents are typical CO2 capture routes. However, amine-solution absorption normally consumes substantial amounts of energy, and supported-amine adsorption suffers from low capture capacity. Herein, a CaCl2-supported amine adsorbent was prepared to combine the high capture capacity and low energy consumption of a packed-bed system. Gas- and solid-phase models coupled with a changing-particle-size model were developed to predict the adsorption/desorption behavior. A new index of synergy angle distribution gradient (SADG) was used to characterize the synergistic effects. Experiments were performed to determine the adsorption/desorption reaction kinetics and validate the model. The improved field synergy theory determined that diffusion and reaction dominated the CO2 capture by the CaCl2-supported amine adsorbent. This process improved the capture capacity and energy consumption by 30% and 10%, respectively, compared to the conventional CO2 capture process.