Preparation and carbon dioxide uptake capacity of N-doped porous carbon materials derived from direct carbonization of zeolitic imidazolate framework

The preparation, characterization and CO₂ uptake performance of N-doped porous carbon materials and composites derived from direct carbonization of ZIF-8 under various conditions are presented for the first time. It is found that the carbonization temperature has remarkable effect on the compositions, the textural properties and consequently the CO₂ adsorption capacities of the ZIF-derived porous materials. Changing the carbonization temperature from 600 to 1000 °C, the composites and the resulting porous carbon materials possess a tuneable nitrogen content in the range of 7.1-24.8 wt%, a surface area of 362-1466m² g^-1 and a pore volume of 0.27-0.87 cm3 g^-1, where a significant proportion of the porosity is contributed by micropores. These N-doped porous composites and carbons exhibit excellent CO₂ uptake capacities up to 3.8 mmol g^-1 at 25 °C and 1 bar with a CO₂ adsorption energy up to 26 kJ mol^-1 at higher CO₂ coverages. The average adsorption energy for CO₂ is one of the highest ever reported for any porous carbon materials. Moreover, the influence of textural properties on CO₂ capture performance of the resulting porous adsorbents has been discussed, which may pave the way to further develop higher efficient CO₂ adsorbent materials.