Tuning CO₂ Binding in Metal–Organic Framework Materials by Varying Metal Identity and Oxidation State

Abstract

CO2 adsorption from distributed and point sources has attracted significant interest in the recent past, and advanced sorbent design remains a fruitful avenue of research, yet structure–property relationships that capture the effect of an adsorption site coordination environment on binding characteristics remain (for the most part) elusive. Metal–organic framework (MOF) materials carry adsorption sites in highly well-defined coordination environments and present an opportunity for relating specific features of an open-metal coordination environment (such as oxidation state) with sorbate binding characteristics. In this work, we investigate CO2 adsorption onto isostructural Al-, Fe-, and Cr-containing MIL-100­(M) materials to clearly demonstrate the oxidation state-dependent binding of CO2 to some metals but not others. Specifically, Cr2+ sites on MIL-100 nodesfound challenging to access in the prior literatureare demonstrated to exhibit remarkably stronger binding to CO2 compared to their Cr3+ counterparts. Results presented provide a template for tuning CO2 adsorption properties by systematically varying metal identity and oxidation state in MOFs specifically and CO2 capture sorbents more generally.

Minireview and Perspectives of Bimetallic Metal–Organic Framework Electrocatalysts for Carbon Dioxide Reduction

“…44 On the one hand, the choice of metal needs to consider valence and coordination ability. 45 On the other hand, acidic-stable MOFs can be obtained by choosing to introduce high-priced metals (hard acids, such as Zr 4+ and Al 3+ ). Low-cost metals (soft acids, such as Co 2+ and Ni 2+ ) were combined to synthesize alkaline-resistant MOFs.…”

“…The 3D orbital electronic structure of active sites of the bimetallic MOF was modulated, thus favoring the adsorption of the intermediate . On the one hand, the choice of metal needs to consider valence and coordination ability . On the other hand, acidic-stable MOFs can be obtained by choosing to introduce high-priced metals (hard acids, such as Zr 4+ and Al 3+ ).…”

Designing Carbon‐Based Porous Materials for Carbon Dioxide Capture

“…[256,257] Many articles confirmed that metal cations can be simply introduced into adsorbents via chemical reduction and cation exchange. [258,259] Such metal sites enable the easy approach of CO 2 molecules toward the pore surfaces and improve the gas-adsorbent interactions. Due to the high polarity and quadrupole moment of CO 2 , the selectivity is also enhanced over high-affinity binding sites.…”