Sulfur- and Nitrogen-Incorporated Phenothiazine-Based Porous Organic Polymer: Selective and Efficient CO₂ Capture and Evaluation for Vacuum Swing Adsorption

Carbon capture and storage (CCS) is considered an effective strategy for reducing CO2 emissions and addressing climate change. We report the synthesis of rigid, robust phenothiazine and 3D triptycene-containing microporous polymer (NS-TMP) possessing nitrogen and sulfur heteroatoms via a one-pot facile Friedel–Crafts reaction as an efficient microporous adsorbent for selective CO2 capture. The incorporation of triptycene units in the NS-TMP polymer structure imparts several advantageous characteristics, including inherent microporosity, increased surface area, and enhanced thermal stability. NS-TMP exhibits significant micropore volume, a BET-specific surface area (SABET) of 863 m2/g, and promising thermal stability (Td = 321 °C). Additionally, the presence of phenothiazine units containing N and S heteroatoms enhances its ability for selective CO2 capture. NS-TMP demonstrates a strong affinity for CO2, with a heat of adsorption (Qst) of 35 kJ/mol, indicating an excellent CO2 adsorption capacity, significantly influenced by the micropore volume. The selectivity for CO2/N2 and CO2 over CH4 for NS-TMP was estimated to be reasonably high, reaching values of 72 and 11, respectively, showcasing its potential for effective CO2 separation in various applications. Furthermore, Grand Canonical Monte Carlo (GCMC) simulation was conducted to study the adsorption of CO2 in NS-TMP. Using the isotherm data, performance indicators for a cyclic vacuum swing adsorption (VSA) process were measured to estimate the practical suitability of NS-TMP.