Amine–Oxide Hybrid Materials for CO₂ Capture from Ambient Air

Abstract

Oxide supports functionalized with amine moieties have been used for decades as catalysts and chromatographic media. Owing to the recognized impact of atmospheric CO2 on global climate change, the study of the use of amine-oxide hybrid materials as CO2 sorbents has exploded in the past decade. While the majority of the work has concerned separation of CO2 from dilute mixtures such as flue gas from coal-fired power plants, it has been recognized by us and others that such supported amine materials are also perhaps uniquely suited to extract CO2 from ultradilute gas mixtures, such as ambient air. As unique, low temperature chemisorbents, they can operate under ambient conditions, spontaneously extracting CO2 from ambient air, while being regenerated under mild conditions using heat or the combination of heat and vacuum. This Account describes the evolution of our activities on the design of amine-functionalized silica materials for catalysis to the design, characterization, and utilization of these materials in CO2 separations. New materials developed in our laboratory, such as hyperbranched aminosilica materials, and previously known amine-oxide hybrid compositions, have been extensively studied for CO2 extraction from simulated ambient air (400 ppm of CO2). The role of amine type and structure (molecular, polymeric), support type and structure, the stability of the various compositions under simulated operating conditions, and the nature of the adsorbed CO2 have been investigated in detail. The requirements for an effective, practical air capture process have been outlined and the ability of amine-oxide hybrid materials to meet these needs has been discussed. Ultimately, the practicality of such a "direct air capture" process is predicated not only on the physicochemical properties of the sorbent, but also how the sorbent operates in a practical process that offers a scalable gas-solid contacting strategy. In this regard, the utility of low pressure drop monolith contactors is suggested to offer a practical mode of amine sorbent/air contacting for direct air capture.

Oxidation‐Resistant, Cost‐Effective Epoxide‐Modified Polyamine Adsorbents for CO2 Capture from Various Sources Including Air

“…Some of the most studied adsorbents for DAC are solid hybrid adsorbents based on polyamines impregnated or chemically bound on supports including silica, mesoporous solids (SBA‐15, MCM‐41, MCM‐48, etc. ), hyperbranched silicas (HAS), alumina, various polymers, carbon, and carbon fibers . Our group reported, for example, the straightforward and simple preparation and use of both LPEI and BPEI impregnated on precipitated and fumed silica as superior adsorbents for DAC under dry and humid conditions …”

Solid‐State Gas Adsorption Studies with Discrete Palladium(II) [Pd2(L)4]4+ Cages

“…This last role is of increasing importance as part of concerted efforts to capture carbon dioxide and lower carbon emissions, and many MOFs have been shown to adsorb CO 2 . In particular, it has been shown that internal functionalization of MOFs with amine groups can result in highly impressive CO 2 uptake and storage …”

Technologien zur Speicherung von Wasserstoff. Teil 2: Irreversible Konversion und Technologievergleich

“…[5] Die Anforderungen an die Reinheit von CO 2 aus der Luft für Sabatier-oder Fischer-Tropsch-Prozesse sind deutlich höher [6,7]. Nichtsdestotrotz sollte berücksichtigt werden, dass die Abtrennung aus der Luft wegen der geringen Konzentration sehr aufwendig ist.…”