As promising adsorbents in carbon capture and storage, hyper-cross-linked polymers (HCPs) require high CO2 uptake and selectivity over N-2 and CH4. Herein, we reported a series of novel carbonyl-incorporated HCPs using oxalyl chloride as a cross-linker. To enhance the CO2 adsorption capacity and gas selectivity, the fabricated HCPs were further modified by methods of amine functionalization (HCPs-N) and KOH activated carbonization (HCPs- C). Accordingly, the maximum CO2 adsorption capacity of HCPs (HCP3) reaches 198 mg/g owing to abundant carbonyl groups and dominant microporous structures (S(BET)1047 m(2)/g, S(micro)628 m(2)/g). Meanwhile, under the effect of amine functionalization, the selectivity of the obtained HCPs-N (HCP3-N) is greatly improved, reaching a maximum of 85.71 (SCO2/N-2) and 8.12 (SCO2/CH4). Furthermore, after KOH activated carbonization, the amount of CO2 adsorption of HCPs-C (HCP3-C) significantly increases to 270 mg/g due to the higher specific surface area (S(BET)1421 m(2)/g) and arising ultramicroporous structures (V(ultra)0.26 cm(3)/g). Aromatic polymers with microporous structures and carbonyl group can be prepared and functionalized to improve the CO2 adsorption and gas selectivity by simple and mild reactions. Our study provides new options for CO2 capture of HCPs and provides a new idea for the synthesis of new HCPs.