Capture of CO₂ from the air offers a promising approach to managing carbon levels and achieving carbon neutrality goals. For capturing CO₂ from a highly dilute source (400 ppm), a durable material with high capacity, rapid kinetics, and a low regeneration temperature is required. We report a covalent organic framework (COF) and a covalent modification strategy leading to a class of promising CO₂ capture materials. Specifically, a porous, crystalline (COF) with olefin linkages has been synthesized, structurally characterized, and post-synthetically modified by the covalent attachment of amine initiators for producing polyamines within the pores. The resulting COF (COF-999) takes up 2.05 mmol g^–1 CO₂ under direct air capture (DAC) related conditions (400 ppm of CO₂ in the air with 50% relative humidity), making it stand out from the current state-of-the-art materials. The adsorption kinetics of COF-999 (r_max = 0.11 mmol g⁻¹ min⁻¹, and reaches half capacity within 18.8 min) are one of the fastest observed. Additionally, the adsorbed CO₂ can be easily desorbed at 60 °C, which is lower than common DAC materials (typically > 110 °C). We evaluated the viability of the COF by using outdoor air in Berkeley, California as the CO₂ source with 100 adsorption-desorption cycles and found COF-999 fully retained its performance, making COF-999 one of the most stable carbon capture materials to work repeatedly under open air conditions. With this study, we used COF chemistry as platform and demonstrated a new design and synthesis strategy which could lead to a large class of carbon capture materials.

Zihui Zhou

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