Heating of a high carbon-containing metal salt under nitrogen generates microporous carbons with exceptional post-combustion CO₂ capture ability. Depending on carbonisation temperature (600–1000 °C) and duration (0.5 to 4 h), microporous carbons with surface area and pore volume of 500–2100 m² g⁻¹ and 0.27–1.1 cm³ g⁻¹, respectively, are generated. The proportion of microporosity is high; 96% of surface area and up to 92% of pore volume. The porosity is dominated by 6–7 Å pores, which is advantageous for CO₂ uptake; the carbons capture up to 4.8 mmol g⁻¹ at 1 bar and 25 °C. Under post-combustion flue gas stream conditions (0.15 bar CO₂), the carbons capture up to 1.7 mmol g⁻¹ of CO₂, which is the highest so far reported for porous carbons. The carbons have excellent selectivity for CO₂ over N₂; a selectivity factor of 43 based on CO₂ and N₂ initial adsorption rates, an Ideal Adsorbed Solution Theory (IAST) selectivity factor of 50 and an equilibrium CO₂/N₂ adsorption ratio at 1 bar of 22.5 compared to typical values of 5–11 for carbons. Moreover, the carbons show excellent CO₂ uptake for low pressure swing operations; working capacity of up to 5.4 and 3.4 mmol g⁻¹ for pressure swing adsorption (PSA) from a pure CO₂ stream (6 to 1 bar) and flue gas stream (1.2 to 0.2 bar), respectively. The working capacity for vacuum swing adsorption (VSA) is even more remarkable; reaching 5.1 and 2.4 mmol g⁻¹ under pure CO₂ (1.5 to 0.05 bar) and flue gas (0.3 to 0.01 bar) conditions, respectively. The carbons also have excellent working capacity for temperature swing adsorption (TSA). The carbons are readily densified to high packing density of up to 1.12 g cm⁻³ with no penalties on textural properties or gravimetric CO₂ uptake. The densification and high gravimetric uptake, gives exceptional volumetric CO₂ capture capacity of 71, 187 and 320 g l⁻¹ at 0.15, 1 and 5 bar, respectively, and unrivalled working capacity for PSA, VSA and TSA processes. The simple synthesis route, optimal pore size and exceptional CO₂ uptake means that the carbons offer an unprecedented combination of characteristics for post-combustion CO₂ capture.