The capture of sulfur dioxide (SO2) using dehydrated Na-6[AlSiO4](6) sodalite was investigated using the first principles density functional theory calculations and thermodynamics analysis. The adsorption geometries, energetics, and electronic structures were predicted with the increasing number of SO2 adsorbates. Upon adsorption, the S atom of single SO2 molecule tends to align to the framework O2- and the two oxygen atoms are oriented to the framework Na+, through electrostatic interactions and with a minor charge transfer. Increasing the number of SO2 adsorbates, the Na-6[AlSiO4](6) sodalite framework shrinks first and then expands. Statistical thermodynamics analysis suggests that the capture reaches its saturation limit of four SO2 molecules per Na-6[AlSiO4](6) formula (300mg/g) at room temperature and a low SO2 partial pressure of 0.001atm, indicating that dehydrated Na-6[AlSiO4](6) can be an efficient SO2 sorbent even at its extremely low concentrations. Higher SO2 partial pressures lead to a higher capture capacity. A low baking temperature of 100-150 degrees C can efficiently release the adsorbed SO2 and hence restore the capture capacity of Na-6[AlSiO4](6).