Excessive emission of greenhouse gases has caused global warming and been seriously damaging the ecological environment. Adsorption technology is one of the most powerful methods widely used for carbon capture. However, the currently available rigid porous adsorbents are all insoluble, the regeneration of which once blocked is a quandary. In this study, we synthesized a soluble polymeric adsorbent of intrinsic microporosity (AO-PIM-1) for carbon dioxide (CO2) capture. The adsorbent of AO-PIM-1, an amidoxime functionalized PIM-1, possesses a high-specific surface area of 503 m2/g and a strong affinity for CO2 with the heat of adsorption of 30.6 kJ/mol. It exhibits high CO2 adsorption capacity and CO2/N2 selectivity evidenced by computational calculations and experimental breakthrough experiments. More importantly, the microporous AO-PIM-1 is well soluble in common organic solvents like DMF, DMSO, and DMAc, but insoluble in methanol, which allows the regeneration, once being fouled, with a solvent dissolution-separation purification-nonsolvent-induced precipitation (DSP) method.