Direct synthesis of organic salt-derived porous carbons for enhanced CO2 and methane storage

Abstract

The direct carbonisation of a carbon-rich organic salt, potassium phthalimide (PPI), generates porous carbons with porosity suitable for energy-related gas storage applications. The PPI-derived carbons exhibit high surface area of up to 2889 m² g⁻¹ and pore volume of up to 1.36 cm³ g⁻¹, and the porosity can be readily tailored by choice of the carbonisation temperature and, to a lesser extent, carbonisation time. Depending on the preparation conditions, the PPI-derived carbons can be tailored to have ideal porosity for CO₂ uptake at low pressure, which at 25 °C reaches 1.7 mmol g⁻¹ and 5.2 mmol g⁻¹ at 0.15 bar and 1 bar, respectively. The carbons also exhibit very impressive methane storage capacities of up to 18.2 mmol g⁻¹ at 25 °C and 100 bar. An important finding is that the carbons may be readily compacted to a high packing density of up to 1.10 g cm⁻³ with retention of their textural properties. The consequence of the high packing density of the PPI-derived carbons, coupled with their high gravimetric methane uptake, is that they achieve exceptionally high volumetric uptake of up to 338 cm³ (STP) cm⁻³ at 25 °C and 100 bar, and volumetric working capacity (100–5 bar pressure swing) of 249 cm³ (STP) cm⁻³, which are significantly higher than most porous carbons and metal–organic frameworks (MOFs). PPI is thus a very attractive precursor for the simple synthesis of porous carbons with an unrivalled mix of properties for CO₂ and methane storage applications.