Decoding Carbon-Based Materials' Properties for High CO₂ Capture and Selectivity

Carbon-based materials are well established as low-cost, easily synthesizable, and low regeneration energy adsorbents against harmful greenhouse gases such as CO₂. However, the development of such materials with exceptional CO₂ uptake capacity needs well-described research, wherein various factors influencing CO₂ adsorption need to be investigated. Therefore, five cost-effective carbon-based materials that have similar textural properties, functional groups, and porous characteristics were selected. Among these materials, biordered ultramicroporous graphitic carbon had shown an excellent CO₂ capture capacity of 7.81 mmol/g at 273 K /1 bar with an excellent CO₂ vs N₂ selectivity of 15 owing to its ultramicroporous nature and unique biordered graphitic morphology. On the other hand, reduced graphene revealed a remarkable CO₂ vs N₂ selectivity of 57 with a CO₂ uptake of 2.36 mmol/g at 273 K/1 bar. In order to understand the high CO₂ capture capacity, important properties derived from adsorption/desorption, Raman spectroscopy, and X-ray photoelectron spectroscopy were correlated with CO₂ adsorption. This study revealed that an increase in ultramicropore volume and sp² carbon (graphitic) content of nanomaterials could enhance CO₂ capture significantly. FTIR studies revealed the importance of oxygen functionalities in improving CO₂ vs N₂ selectivity in reduced graphene due to higher quadruple-dipole interactions between CO₂ and oxygen functionalization of the material. Apart from high CO₂ adsorption capacity, biordered ultramicroporous graphitic carbon also offered low regeneration energy and excellent pressure swing regeneration ability for five consecutive cycles.