Pore Wall Engineered Polar COFs as Size‐Matched Nanotraps Enable Highly Efficient Capture of Long‐Chain Alkylamines

Abstract

Long‐chain alkylamines are widely used as surfactants and inevitably cause environmental pollution. However, there is still a lack of adsorbents that can efficiently remove them due to the scarcity of available binding sites. Herein, this study demonstrates that pore wall‐engineered polar covalent organic frameworks (COFs) with tailored pore size can be used as promising nanotraps for the rapid and highly efficient capture of octadecylamine (ODA, a typical long‐chain alkylamine) from complex practical samples (e.g., salt lake brine). Under the optimized conditions, nitro‐functionalized COFs (TpPa‐NO2 and TpBD‐NO2) show much better ODA adsorption performances than unfunctionalized TpPa, and TpPa‐NO2, whose pore size matches the ODA molecule best, obtained an ODA adsorption capacity as high as 128.5 mg g−1 within 20 min. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations elucidate the underlying adsorption mechanisms, revealing that COFs provide multiple interaction forces, including electrostatic, polar, van der Waals, hydrogen bond, hydrophobic, and C─H σ–π interactions, which synergistically contribute to the highly efficient capture of ODA in the 1D polar nanotraps of TpPa‐NO2. This study provides a theoretical foundation and experimental evidence for utilizing COFs as long‐chain alkylamine adsorbents and offers a strategy for designing functionally tailored COFs for environmental applications.