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 CO 2 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 CO 2 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 (SA BET ) of 863 m 2 /g, and promising thermal stability ( T d = 321 °C). Additionally, the presence of phenothiazine units containing N and S heteroatoms enhances its ability for selective CO 2 capture. NS-TMP demonstrates a strong affinity for CO 2, with a heat of adsorption ( Q st ) of 35 kJ/mol, indicating an excellent CO 2 adsorption capacity, significantly influenced by the micropore volume. The selectivity for CO 2 /N 2 and CO 2 over CH 4 for NS-TMP was estimated to be reasonably high, reaching values of 72 and 11, respectively, showcasing its potential for effective CO 2 separation in various applications. Furthermore, Grand Canonical Monte Carlo (GCMC) simulation was conducted to study the adsorption of CO 2 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.