Defect-rich Mg-Al MMOs supported TEPA with enhanced charge transfer for highly efficient and stable direct air capture

Abstract

Due to the advantages of low energy consumption and high CO2 selectivity, the development of solid amine-based materials has been regarded as a hot research topic in the field of DAC for the past decades. The adsorption capacity and stability over multiple cycles have been the top priorities for evaluation of practical application value. Herein, we synthesized a novel DAC material by loading TEPA onto defect-rich Mg0.55Al-O MMOs with enhanced charge transfer effect. The optimal Mg0.55Al-O-TEPA67% demonstrates the highest CO2 uptake of (3.0 mmol g−1) and excellent regenerability, maintaining ∼90% of the initial adsorption amount after 80 adsorption/desorption cycles. The in situ DRIFTS experiments suggested the formation of bicarbonate species under wet conditions. DFT calculations indicated that the stronger bonding between Mg0.55Al-O support and solid amine was caused by the abundance of oxygen defects on MMOs confirmed by XPS and ESR, which favors the charge transfer between the support and amine, resulting in intense interaction and excellent regenerability. This work for the first time conducted comprehensive and systematic investigation on the stabilization mechanism for MMOs supported solid amine adsorbents with highest uptake and superior cyclic stability in depth, which is different from the most popular SiO2-support, thus providing facile strategy and comprehensive theoretical mechanism support for future research about DAC materials.