The steady rise in atmospheric CO2 levels has led to a serious environmental threat in the form of global warming and climate change. Therefore, the development of efficient porous nanomaterials as adsorbent and catalyst that simultaneously capture CO2 and catalytically convert it into value-added chemicals is a very challenging area of research today. Herein, we report the synthesis of three nitrogen-rich, aminal-linked porous organic polymers (POPs), namely, TBAL-POP-3, TBAL-POP-4, and TBAL-POP-5, constructed via extended Schiff-base condensation reaction under solvothermal conditions. Among the three polymers, TBAL-POP-5 exhibits the highest specific surface area (1053 m2 g−1), highest fraction of hierarchical mesopores (84%), and high CO2 uptake capacity of 1.92 mmol g−1 at 273 K and 1 bar and good CO2/N2 selectivity 43.82/32.03 at 273/298 K. The enhanced gas adsorption performance of TBAL-POP-5 is attributed to its mesopore-enriched hierarchical structure, which facilitates efficient mass transfer and active site accessibility. Furthermore, these materials demonstrated good catalytic activity toward the formylation of amines using CO2 as a sustainable C1 source in the presence of dimethylamine borane as a green reducing agent. This work highlights the dual functionality of nitrogen-rich porous polymers as multifunctional platforms for integrated CO2 capture and its reductive valorization.