In-situ construction of CNF@ZIF-8 precursors via templating for N-doped porous carbon with CO2/N2 selective adsorption

To develop high-efficiency carbon dioxide (CO 2 ) adsorbents featuring low-pollution and low-energy-consumption preparation, gel bead precursors were first fabricated via gelation of nanocellulose, polyvinyl alcohol (PVA), and 2-methylimidazole. A nitrogen-doped precursor derived from hydrothermal recrystallization of melamine and dextrin was uniformly incorporated into the gel matrix to construct a nitrogen-enriched system. Subsequently, ZIF-8 was grown in situ within the composite beads through immersion in a zinc ion solution, yielding a biomass-polymer@ZIF-8 support after drying, which was then carbonized under N 2 to produce nitrogen-doped porous carbons. Based on static CO 2 adsorption evaluations across 15 sample sets at 0 ℃ and 25 ℃, 800 °C was identified as the optimal carbonization temperature. The sample CZN-II-800, with 4.31% external nitrogen doping in the precursor, exhibited absolute CO 2 adsorption capacities of 3.39 mmol/g at 0 ℃ and 3.08 mmol/g at 298 K (1 bar), which was 66.5% higher than that of its nitrogen-free counterpart CZ-800. Additionally, it displayed a CO 2 /N 2 selectivity coefficient of 8.9 under dynamic competitive adsorption conditions at 1 bar and 298 K. This work therefore establishes a scalable hybrid route integrating biomass materials with ZIFs to design high-performance adsorbents for efficient CO 2 capture from flue gases.