Sulfhydryl‐Mediated Thermal Stabilization of Nitrogen Adsorption Sites in Aromatic Heterocyclic Waste‐Derived Activated Carbon for Enhanced CO ₂ Capture

Abstract Thermally unstable nitrogen sites impede the synthesis of porous carbons with balanced porosity and surface chemistry for efficient CO ₂ capture. Using benzimidazole as a model system, this work examines the viability of molecular engineering approaches to improve the thermal stability of aromatic heterocyclic waste materials under high‐temperature activation conditions. By integrating machine learning‐guided feature importance analysis, nitrogen content quantification, and bond dissociation energy calculations, we identify N‐doping percentage as the critical determinant of CO ₂ adsorption capacity and reveal that sulfhydryl‐substituted benzimidazole exhibits higher thermal stability of nitrogen adsorption sites. This modification strengthens intramolecular bonding within the Imidazole ring. The sulfhydryl‐functionalized precursor retained a high nitrogen content of 9.66 at% even at 700 °C, resulting in the derived NS700 material achieving a CO ₂ adsorption capacity of 5.48 mmol g ⁻¹ at 25 °C and 1 bar, which is 65% higher than its unmodified counterpart. Comparative analysis of nitrogen content in four base molecules and their sulfhydryl‐substituted derivatives, combined with molecular dynamics simulations and HOMO‐LUMO gap calculations, visually demonstrates that sulfhydryl substitution enhances thermal stability during high‐temperature activation for activated carbon production, thereby improving nitrogen retention rates. This work establishes that molecular structure design optimizes activated carbon preparation from aromatic heterocyclic waste.