Direct Air Capture and Sequestration of CO2 with a Tailored Hybrid Anion Exchanger: Novel Use of Seawater as a Primary Regenerant and an Infinite Sink

[Geoengineering News]

https://pubs.acs.org/doi/abs/10.1021/acs.iecr.6c00025

Authors: Xinkai Wu, Hao Chen, Haibo Liu, Arup K. Sengupta

29 April 2026

Abstract 

Direct air capture (DAC) offers a pathway for negative carbon emissions but remains constrained by a high desorption energy demand and uncertain long-term global CO2 storage. Here, we present for the first time a robust and sustainable DAC alternative using a tailored decarbonizing hybrid anion exchanger or D-HAIX. The D-HAIX is a polymer-based solid ion exchanger that i) exhibits very high CO2 capture capacity under ambient conditions; ii) is amenable to efficient regeneration or desorption with seawater through Cl––HCO3– anion exchange, and iii) is also durable over hundreds of cycles. Spent regenerant, with practically no change in salinity, may be returned to seawater, as no adverse effects were observed in the tested marine organisms. Other CO2 sorbents reported to date, such as weak base amines, metal-organic frameworks (MOFs), modified zeolites, etc., are mechanistically and operationally inappropriate for salt regeneration. Additionally, the proposed process avoids underground geological storage and uses oceans as infinite sinks. Tens of other countries may deploy this DAC technology in areas where geological storage is unavailable or uncertain. The use of D-HAIX with seawater as a regenerant and a potential sink may broaden DAC deployment opportunities, particularly in coastal regions where geological storage is unavailable or uncertain.

Source: ACS Publications