Tailored N-doped porous carbon via a MOF assembly process for high-performance CO2 uptake

Striking a balance between the nitrogen content and pore texture of N-containing metal–organic framework (MOF)-derived carbon is a considerable challenge for high-performance CO2 capture. The high-temperature pyrolysis and activation facilitated well-developed pore structures but resulted in serious nitrogen loss of MOFs. In this work, we developed MOF (ZIF-8)-derived N-doped porous carbons (NPCs) by integrating ZIF-8 with pomelo peel via a co-carbonization and activation process to construct a high-performance CO2 adsorbent. The pomelo peel can effectively prevent the nitrogen loss from the ZIF-8 backbone via pre-melting and polymerization and simultaneously offer the ideal porosity and BET surface area during the co-carbonization and activation process. By tuning the ZIF-8 loading capacity and the activation temperature, the sample NPC-800-4 prepared at 800 °C possessed both ultrahigh surface area (∼1967 m2 g−1) and high N content (∼13.15 wt%). Particularly, the CO2 capacity of NPC-800-4 reached 5.51 mmol g−1 at 25 °C and 9.01 mmol g−1 at 0 °C under 1 bar due to its relatively high content of pyrrolic-N (N5 ∼ 61.2%) and pyridinic-N (N6 ∼ 16.5%), as well as the proper pore size distribution (0.64 nm). In addition, the TPD measurement and CO2 adsorption energy (Qst) of NPC-800-4 also suggested the high desorption activation temperature and energy, indicating a strong binding capacity toward CO2. Moreover, NPC-800-4 exhibited almost constant CO2 uptake in 8 consecutive adsorption–desorption cycles, indicating that the sample with great stability and recyclability would be easily adapted and recycled from industries. This co-carbonization and activation strategy to assembly MOFs with biomass would pave the way for enhancing CO2 capture of MOF-derived carbons.