Microporous carbon nanoflakes derived from biomass cork waste for CO₂ capture

Porous structure design is considered to be a promising strategy for the development of effective sorbents for CO₂ capture. Herein, a series of carbon nanoflakes with large surface area (up to 2380 m²/g) and high micropore volume (up to 0.896 m³/g) were synthesized from a renewable precursor, cork dust waste, to capture CO₂ at atmospheric pressure. The nanoflakes exhibited superior CO₂ uptake performance at 1 bar with the maximum capacity of 7.82 and 4.27 mmol/g at 0 and 25 °C, respectively, in sharp contrast to previously reported porous carbon materials. The existence of large numbers of narrow micropores with the pore width less than 0.86 nm and 0.70 nm play a critical role in the CO₂ uptake at 0 and 25 °C, respectively. Moreover, the CNFs exhibited good recyclability and high selectivity for CO₂ uptake from the mixture of CO₂ and N₂. By taking advantage of the unique hollow honeycomb cell, the three-layered cell wall structure, as well as the unique chemical composition of a cork precursor, such delicate microporous carbon nanoflakes were able to be achieved by simple thermal pretreatment combined with chemical activation. This bioinspired precursor-synthesis route poses a great potential for the facile production of porous carbons for a variety of diverse applications including CO₂ capture.