Facile synthesis of structured adsorbent with enhanced hydrophobicity and low energy consumption for CO2 capture from the air

Summary

Formulating materials into structured configurations is important to improve CO₂ capture efficiency. Here, the hydrophobic polystyrene-block-polybutadiene-block-polystyrene (SBS) is used as the binder to coat polyethyleneimine (PEI) mesoporous cellular foam (MCF) onto ceramic fiber honeycombs. It not only makes the powder attach stably and uniformly on the honeycomb but also maintains the porosity for favorable CO₂ diffusion. The synthesis was optimized, and a capacity of 0.71 mmol g⁻¹ composite (or 2.33 mmol g⁻¹ adsorbent) in 400 ppm CO₂ is presented. The SBS endows the structured adsorbent with enhanced hydrothermal stability, as verified by the steam purge and accelerated stability experiments. Additionally, it remained stable throughout 100 cycles and kept mechanically robust under air blowing. Simulations of steam-assisted temperature vacuum swing adsorption (S-TVSA) processes demonstrate its high CO₂ productivity of 5.60 mol kg⁻¹ day⁻¹ and low energy consumption of 0.196 MJ mol⁻¹. These findings, together with the low cost and facile synthesis of the adsorbent, make it a promising candidate for direct air capture (DAC) scale-up deployments.