High‐Performance CO₂ Capture from Air by Harnessing the Power of CaO‐ and Superbase‐Ionic‐Liquid‐Engineered Sorbents

Abstract

Direct air capture (DAC) of CO2 by solid porous materials represents an attractive “negative emission” technology. However, state‐of‐the‐art sorbents based on supported amines still suffer from unsolved high energy consumption and stability issues. Herein, taking clues from the CO2 interaction with superbase‐derived ionic liquids (SILs), high‐performance and tunable sorbents in DAC of CO2 was developed by harnessing the power of CaO‐ and SIL‐engineered sorbents. Deploying mesoporous silica as the substrate, a thin CaO layer was first introduced to consume the surface‐OH groups, and then active sites with different basicities (e. g., triazolate and imidazolate) were introduced as a uniformly distributed thin layer. The as‐obtained sorbents displayed high CO2 uptake capacity via volumetric (at 0.4 mbar) and breakthrough test (400 ppm CO2 source), rapid interaction kinetics, facile CO2 releasing, and stable sorption/desorption cycles. Operando diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) analysis under simulated air atmosphere and solid‐state NMR under 13CO2 atmosphere demonstrated the critical roles of the SIL species in low‐concentration CO2 capture. The fundamental insights obtained in this work provide guidance on the development of high‐performance sorbents in DAC of CO2 by leveraging the combined advantages of porous solid scaffolds and the unique features of CO2‐philic ionic liquids.

From Lab to Fab: Development and Deployment of Direct Air Capture of CO2

“…Attaching CO2-philic functional groups to ILs can dramatically enhance their CO2 collection ability [41]. Moitra et al [43] used CaO-and superbase-ionic liquids (SIL)-bifunctionalized sorbents to capture CO2; these sorbents demonstrated rapid interaction kinetics, high CO2…”

“…Attaching CO 2 -philic functional groups to ILs can dramatically enhance their CO 2 collection ability [41]. Moitra et al [43] used CaO-and superbase-ionic liquids (SIL)-bifunctionalized sorbents to capture CO 2 ; these sorbents demonstrated rapid interaction kinetics, high CO 2 uptake capacity, facile CO 2 release, and stable sorption/desorption cycles. New research proposes that immobilizing ILs in porous materials with large surface areas and specific active sites, such as MOFs, might remedy the difficulties caused by ILs [44][45][46], which is discussed further in the MOF part under Section 2.2.…”

Minimal Kinetic Model of Direct Air Capture of CO2 by Supported Amine Sorbents in Dry and Humid Conditions

“…2,23−25 Moreover, other chemisorption systems using superbase-derived ionic liquids have been developed. 26,27 Although researchers have turned their attention to DAC conditions, 8,28,29 how sorbent properties and H 2 O affect CO 2 adsorption at DAC conditions is not well understood from a modeling perspective. 30−32 On the experimental side, Sayari, 33 Jones, 1 and many others have extensively examined aminefunctionalized mesoporous silica for DAC.…”

“…The dilute concentration of CO 2 in ambient air at about 400 ppm is one major challenge for DAC, requiring a strong thermodynamic driving force for its sorption. Most of the experimental and modeling work on amines focused on much higher CO 2 partial pressures. ,− Enhanced CO 2 adsorption in the presence of H 2 O has been widely observed in amine adsorbents. ,− Moreover, other chemisorption systems using superbase-derived ionic liquids have been developed. , Although researchers have turned their attention to DAC conditions, ,, how sorbent properties and H 2 O affect CO 2 adsorption at DAC conditions is not well understood from a modeling perspective. − On the experimental side, Sayari, Jones, and many others have extensively examined amine-functionalized mesoporous silica for DAC. The effect of water on CO 2 adsorption has been recently reviewed by Sayari and co-workers, while Jones and co-workers have investigated many different types of porous supports loaded with poly­(ethylenimine) (PEI). , Molecular simulations at both the molecular mechanical and quantum mechanical levels have been employed to understand the DAC of CO 2 and its interaction and reaction with amines as well. − …”