Carbon Dioxide Capture at Nucleophilic Hydroxide Sites in Oxidation-Resistant Cyclodextrin-Based Metal-Organic Frameworks

Abstract

Carbon capture and sequestration (CCS) from industrial point sources and direct air capture are necessary to combat global climate change. A particular challenge faced by amine-based sorbents-the current leading technology-is poor stability towards O-2. Here, we demonstrate that CO2 chemisorption in gamma-cylodextrin-based metal-organic frameworks (CD-MOFs) occurs via HCO3- formation at nucleophilic OH- sites within the framework pores, rather than via previously proposed pathways. The new framework KHCO3 CDMOF possesses rapid and high-capacity CO2 uptake, good thermal, oxidative, and cycling stabilities, and selective CO2 capture under mixed gas conditions. Because of its low cost and performance under realistic conditions, KHCO3 CD-MOF is a promising new platform for CCS. More broadly, our work demonstrates that the encapsulation of reactive OH- sites within a porous framework represents a potentially general strategy for the design of oxidation-resistant adsorbents for CO2 capture.