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 O2. Here, we demonstrate that CO2 chemisorption in γ‐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 CD‐MOF 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.

Fluoroarenes are widely used in medicinal, agricultural, and materials chemistry, and yet their production remains a critical challenge in organic synthesis. Indeed, the nearly identical physical properties of these vital building blocks hinders their purification by traditional methods, such as flash chromatography or distillation. As a result, the Balz−Schiemann reaction is currently employed to prepare fluoroarenes instead of more atomeconomical C−H fluorination reactions, which produce inseparable mixtures of regioisomers. Herein, we propose an alternative solution to this problem: the purification of mixtures of fluoroarenes using metal−organic frameworks (MOFs). Specifically, we demonstrate that controlling the interaction of fluoroarenes with adjacent coordinatively unsaturated Mg 2+ centers within a MOF enables the separation of fluoroarene mixtures with unparalleled selectivities. Liquid-phase multicomponent equilibrium adsorption data and breakthrough measurements coupled with van der Waals-corrected density functional theory calculations reveal that the materials Mg 2 (dobdc) (dobdc 4− = 2,5-dioxidobenzene-1,4-dicarboxylate) and Mg 2 (m-dobdc) (mdobdc 4− = 2,4-dioxidobenzene-1,5-dicarboxylate) are capable of separating the difluorobenzene isomers from one another. Additionally, these frameworks facilitate the separations of fluoroanisoles, fluorotoluenes, and fluorochlorobenzenes. In addition to enabling currently unfeasible separations for the production of fluoroarenes, our results suggest that carefully controlling the interaction of isomers with not one but two strong binding sites within a MOF provides a general strategy for achieving challenging liquid-phase separations.

The Suzuki−Miyaura reaction is one of the most widely employed transformations in synthetic chemistry. Despite extensive investigation, questions remain about the mechanistic nature of the transmetalation step when catalysts based on advanced ligands such as biaryl monophosphines are used, impeding the development of improved catalysts. Here we demonstrate that the often overlooked halide salt (KX) generated as a byproduct of cross-coupling renders the transmetalation step reversible with SPhos-based catalysts, leading to severe reaction inhibition with (hetero)aryl iodides. Stoichiometric and kinetic studies reveal that halide inhibition likely originates from disfavoring the formation of a highly reactive Pd−OH intermediate. We demonstrate that changing the organic solvent in the biphasic reaction mixture from tetrahydrofuran to toluene is sufficient to minimize this inhibition and enable the general Suzuki−Miyaura coupling of (hetero)aryl iodides. Our studies suggest that halide inhibition may be a more general problem in cross-coupling reactions, especially those involving reversible transmetalation processes.

The controlled introduction of defects into MOFs is a powerful strategy to induce new physiochemical properties and improve their performance for target applications. Herein, we present a new strategy for...

Carbon capture and utilization or sequestration and direct air capture will be needed to reduce atmospheric levels of greenhouse gases over the next century. Current aminebased technologies bind CO 2 with high selectivities but suffer from poor oxidative and thermal stabilities. Herein, we discuss understudied sorbents based on oxygen nucleophiles, including metal oxides and hydroxides, hydroxide-containing polymers, and hydroxide-based metal-organic frameworks. In general, these materials display improved oxidative stabilities compared to traditional amine-based sorbents. We outline the challenges and opportunities offered by these alternative sorbents for carbon capture applications.