Next generation solid amine sorbents for scalable direct air capture of carbon dioxide

Abstract

Direct air capture (DAC) is crucial for mitigating climate change by directly removing CO₂ from the atmosphere. However, the large-scale deployment of DAC is hindered by the lack of durable and scalable sorbents and processes especially materials that comply with green synthesis principles. Here, we have applied these principles to develop a simple, scalable method for synthesising a novel sorbent, a nitrogen-rich solid amine network (SAN) with unique structure having an internal mesh size around 0.5 nm. The synthesis is green and can be completed within 10 minutes under ambient conditions. The sorbent showed a CO₂ uptake capacity up to 3.11 mmol g⁻¹ under real-world DAC conditions, nearly three times higher than that of conventional SiO₂-impregnated sorbents. It also demonstrated remarkable resistance to oxidative degradation, retaining over 75% of its capacity after 7 days of accelerated ageing under elevated temperatures (85 °C) in air, while conventional impregnated sorbents and commercially available resins incurred a greater than 50% reduction. In a proof-of-concept DAC scenario assisted by solar, the sorbent was directly exposed to outdoor air and achieved 1 mmol g⁻¹ CO₂ uptake in just 5 hours. This novel sorbent shows promise for large-scale DAC systems by tackling key DAC-associated challenges.