Hydrophobic ZIF-8 covered active carbon for CO2 capture from humid gas

The performance of activated carbon (AC) will be severely affected for carbon dioxide (CO2) capture in flue gas, as they usually suffer from competitive adsorption of water vapor. Establishment of a barrier against moisture on the surface of porous adsorbent material could potentially address this issue. Zeolite-like metal–organic frameworks (ZIF-8) as a promising adsorbent material demonstrates hydrophobic properties, large specific surface area, and highly porous structure. Here, by further growth of ZIF-8 on polydopamine (PDA)-coated bio-based carbon (AC@PDA), we fabricate hydrophobic final product (AC@ZIF-8). The CO2 capture capacities of AC@ZIF-8 was 41.69 cm3/g, which is only 13.61% lower than that of the initial AC under dry conditions. The hydrophobic ZIF-8 layer can effectively prevent water molecules from reaching the interior AC. Therefore, the adsorption of CO2 for AC@ZIF-8 decreased by only 16.74% under high relative humidity, while it decreased by 61.27% for bare AC. This strategy will broaden the applications of carbon-based adsorbents for CO2 capture under severely humid conditions. We believe that this approach is also applicable for an extensive set of CO2 capture materials that suffer from water instability.