Urea-doped hierarchical porous carbons derived from sucrose precursor for highly efficient CO2 adsorption and separation

Abstract

Over the past few years, heteroatom-doped microporous carbons have engrossed significant interest as emergent CO2 adsorbents. However, the clear role of small-sized micropores and heteroatom content on CO2 adsorption is rarely been reported. In this study, a single-step synthetic approach is proposed to prepare a series of sucrose-derived porous carbons by choosing different ratios of KOH and urea (as nitrogen dopant) content (up to ∼ 11 at.%). The role of both KOH and urea variation on textural features (such as specific surface area: SSA, and pore volume: PV) and resultant CO2 adsorption capacity has been studied. Based on KOH and urea content variation, the prepared carbons achieved a remarkable surface area (342-2231 m2g−1), and a large micropore volume (0.24-1.32 cm3g−1). The optimized sample “SUK-113” with sucrose: urea: KOH ratio of 1:1:3 demonstrated a CO2 uptake of 8.19 mmol g−1 at 273K/1 bar. Such remarkable capacity value is accredited to the presence of the highest micropore volume for pores < 1nm for the investigated material. Furthermore, the calculated isosteric heat of adsorption (28.7-34.5 kJ mol−1) and CO2/N2 selectivity (28-137) revealed the significance of nitrogen moieties which offers quadrupole interactions for CO2 molecules and therefore, improved selective separation of CO2 from N2 gases. Conclusively, the narrow micropores and optimum nitrogen content played a decisive role in achieving excellent CO2 adsorption performance in these carbons.