پوريا ياوري

With the increase in population and the subsequent rise in greenhouse gases, the growing need for effective solutions to capture carbon dioxide has led to the development of new absorbent materials. However, developing efficient CO₂ adsorbents with high capacity, stability, and proper regeneration remains a fundamental challenge in environmental and industrial research. Among various materials, periodic mesoporous organosilicas have attracted significant attention due to their tunable porous structures and functionalization capabilities. However, many reported PMOs still suffer from limited efficiency and adsorption, complex synthesis methods, and poor stability and regeneration. In this study, a regular mesoporous organosilica based on thiourea (SC-PMO) was synthesized for the first time using a modified sol-gel method to improve CO₂ adsorption performance. Unlike other PMOs, this method directly incorporates carbamate groups into the porous framework, enhancing adsorption efficiency and surface interactions. Then, its CO₂ adsorption performance was eva‎luated under different pressure and temperature conditions. Considering the limitations of existing adsorption measurement systems (pressure fluctuations, sensor errors, etc.), a custom volumetric adsorption device was designed and built to enhance the accuracy and reliability of the measurements. The new system was validated using zeolite. Thus, the possibility of a very precise performance analysis of SC-PMO was provided. SC-PMO was eva‎luated at five different temperatures (25–45 degrees Celsius) and various pressures (1–7 bar) to assess adsorption isotherms, kinetic behavior, and reduction performance. The results indicate that SC-PMO achieves a maximum adsorption capacity of 2.23 mmol per gram at a pressure of approximately 7 bar and a temperature of 25 degrees Celsius, which demonstrates higher CO₂ adsorption compared to similar adsorbents such as PEI/MCM-48 (0.80 mmol per gram) and PMO-CPF-15 (0.74 mmol per gram) under similar conditions. The adsorption process of SC-PMO was best described by the Sips and Redlich-Peterson models, indicating a heterogeneous surface interaction mechanism with multilayer adsorption. Kinetic eva‎luations also showed that the Elovich and pseudo-second-order models best fit the adsorption process, further reinforcing the material's high interaction energy and surface heterogeneity. The study of adsorbent recovery over ten cycles confirmed that SC-PMO retains its adsorption efficiency with only a minor performance drop (below 5%) and performs better than many reported functional PMOs, which typically show significant capacity loss over repeated cycles. These findings introduce SC-PMO as a competitive CO₂ adsorbent.

جذب سطحي كربن‌دي‌اكسيد , اورگانوسيليكاهاي مزومتخلخل منظم بر پايه‌ي سمي‌كاربازيد , دستگاه اندازه گيري جذب حجمي

Carbon dioxide Adsorption , Semicarbazide-based Periodic Mesoporous Organosilica (SC-PMO) , Volumetric Adsorption

Pooria Yavari

Dr. Shahrokh Shahhosseini