Post-Synthetic Modification of Dibromomethane Knitted Hyper-Cross-Linked Polymers With Sulfonic and Nitro Groups for...

Efficient and selective CO₂ capture represents a crucial technological challenge for carbon emission mitigation in post-combustion processes. This study demonstrates a dual-strategy approach combining high surface area engineering with post-synthetic functionalization (sulfonation and nitration) that breaks the traditional trade-off between adsorption capacity and selectivity in porous polymers for CO₂ capture, thereby simultaneously enhancing CO₂ adsorption capacity and CO₂/N₂ selectivity. We synthesized a hyper-cross-linked polymer (HCP-TPB) using triphenylbenzene (TPB) as a rigid building block and dibromomethane as a cross-linker, achieving exceptional textural properties (BET surface area: 2738 m² g^-1) and CO₂ uptake (21.3 wt% at 273 K). Through post-synthetic sulfonation and nitration, the polymer framework was deliberately engineered to deliver three notable performance improvements: (1) increased CO₂ capacity to 23.7 wt% for HCP-TPB-SO₃H and 23.3 wt% for HCP-TPB-NO₂ at 273 K, (despite reduced surface area (1796 and 1564 m² g^-1) respectively); (2) enhanced CO₂/N₂ selectivity (from 16 for the pristine HCP-TPB to 32 and 42 for HCP-TPB-SO₃H and HCP-TPB-NO₂ at 273 K), and (3) improved Ideal Adsorption Solution Theory (IAST)-predicted selectivity (14→22→35) for 15:85 CO₂/N₂ mixtures at 298 K. These results establish an effective structure-property relationship between sulfonic and nitro functionalities and gas separation performance.