CO2 Adsorption Resins and Solid-Sorption Carbon Capture Processes

2026-10-27 · Carbon Capture · 7 min read

CO2 adsorption resins are amine-functionalized anion exchange resins and hypercrosslinked polymeric sorbents developed for post-combustion capture, biogas upgrading and direct air capture (DAC). Unlike traditional amine solvents, these solid sorbents immobilize amine groups or quaternary ammonium sites on crosslinked polymer skeletons, combining the chemical reaction between amine and CO2 with porous physical adsorption - and avoiding the volatility, corrosion and high regeneration heat penalty of liquid amines.

1. Capture chemistry

For flue-gas capture, weak-base amine resins react with CO2 and water to form bicarbonate and carbamate species. For DAC under very low CO2 partial pressure, quaternary ammonium hydroxide-type resins cycle between hydroxide, carbonate and bicarbonate forms under humidity swing, temperature swing, pH swing or electrochemical swing. Primary and secondary amines provide high reaction activity, while tertiary amine and quaternary ammonium groups improve thermal stability and reduce amine leaching. A macroporous structure speeds gas diffusion and lifts working capacity under humid conditions - moisture is usually beneficial for CO2 uptake on most anion exchange resins.

2. The capture cycle

• Adsorption - humid feed gas (flue gas or ambient air) passes through the resin bed at controlled temperature; CO2 is captured while nitrogen and oxygen pass through
• Saturation - the system switches to regeneration when the bed is spent
• Desorption - typical modes are temperature swing (TSA, 60-90 C), moisture swing (dry purge), electrochemical pH swing and vacuum swing
• Product - desorbed CO2 is collected at better than 95% purity for compression, utilization or sequestration
• Reset - the bed is cooled or re-humidified and returns to the next adsorption cycle

3. Resin sorbents vs liquid amines

4. Challenges and where development is heading

• Equilibrium capacity is still modest at ultra-dilute CO2 concentrations such as ambient air
• Diffusion inside resin beads can be slow - pore engineering matters
• Amine groups degrade gradually under long-term thermal cycling
• Current development focuses on high-density amine grafting, hierarchical pore design and hybrid inorganic-organic resin composites to raise working capacity and cut capture energy

For distributed carbon capture and negative-emission DAC systems, resin sorbents provide a flexible solid-sorption route that scales in modules instead of towers.