Harnessing Oxidized Amines as Robust Sorbents for Carbon Capture

Abstract

Carbon capture and sequestration (CCS) is imperative to mitigating global climate change, but current implementation falls far short of that needed to reach net-zero global emissions by 2050. Aqueous amine solutions, conceived over a century ago, are the current leading technology for CO₂ separations. However, amines suffer from chemical instability under scrubbing conditions, corrosiveness, and toxicity, hindering their long-term implementation at multiton scales. Herein, we demonstrate for the first time that tertiary amine N-oxides, an oxidative degradation product of amines, can remove CO₂ from dilute streams, including flue gas from a natural gas-fired power plant. Our extensive spectroscopic and computational studies support that the nontoxic, noncorrosive, and inexpensive 4-methylmorpholine N-oxide (MMNO) captures CO₂ under humid conditions via the formation of a hydrogen-bond-stabilized bicarbonate (HCO₃^–) species, despite being significantly less basic than an amine. Accelerated aging studies show that MMNO exhibits superior oxidative and thermal stability compared to structurally similar amines, highlighting the potential of eco-friendly N-oxides in industrial carbon capture applications.