Porosity Engineering and Functionalization of Hyper‐Cross‐Linked Polymers for Highly Selective CO2 Adsorption

Abstract Selective carbon dioxide (CO₂) capture from industrial processes is vital for reducing emissions associated with fossil fuel combustion. Achieving both high CO₂ adsorption capacity and excellent CO₂/N₂ selectivity, however, remains a significant challenge. In this study, a novel strategy is introduced that integrates porosity engineering using various cross‐linkers—dimethoxymethane (F), p ‐dichloroxylene (D), and dibromomethane (B)—with post‐synthetic modifications to incorporate nitro (─NO₂) and amino (─NH₂) functional groups into the polymer matrix. Nitration of hyper‐cross‐linked polymer based on dimethoxymethane (HCP‐F) yields HCP‐F‐NO₂, which, upon reduction, produces the amine‐functionalized framework HCP‐F‐NH₂. Both HCP‐F‐NO₂ and HCP‐F‐NH₂ demonstrate relatively high CO₂ uptake. Despite its lower surface area (784 m 2 g⁻¹) compared to HCP‐F‐NO₂ (1066 m 2 g⁻¹), HCP‐F‐NH₂ exhibits superior CO₂/N₂ selectivity of 100, compared to 70 for HCP‐F‐NO₂. Furthermore, ideal adsorbed solution theory (IAST) selectivity calculations at 298 K and 1 bar for 15:85 CO 2 /N 2 confirm enhanced CO 2 /N 2 selectivity after post‐synthetic modification, with HCP‐F‐NH 2 reaching the highest value (64), breakthrough experiments at 298 K with 3 mL min −1 flow rate validate increased CO 2 retention, while regeneration tests confirm structural stability and recyclability, reinforcing the potential of functionalized HCPs for CO 2 capture applications.