Unveiling Unexpected Modulator-CO₂ Dynamics within a Zirconium Metal–Organic Framework

Abstract

Carbon capture, storage, and utilization (CCSU) represents an opportunity to mitigate carbon emissions that drive global anthropogenic climate change. Promising materials for CCSU through gas adsorption have been developed by leveraging the porosity, stability, and tunability of extended crystalline coordination polymers called metal−organic frameworks (MOFs). While the development of these frameworks has yielded highly effective CO 2 sorbents, an in-depth understanding of the properties of MOF pores that lead to the most efficient uptake during sorption would benefit the rational design of more efficient CCSU materials. Though previous investigations of gas−pore interactions often assumed that the internal pore environment was static, discovery of more dynamic behavior represents an opportunity for precise sorbent engineering. Herein, we report a multifaceted in situ analysis following the adsorption of CO 2 in MOF-808 variants with different capping agents (formate, acetate, and trifluoroacetate: FA, AA, and TFA, respectively). In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis paired with multivariate analysis tools and in situ powder X-ray diffraction revealed unexpected CO 2 interactions at the node associated with dynamic behavior of node-capping modulators in the pores of MOF-808, which had previously been assumed to be static. MOF-808-TFA displays two binding modes, resulting in higher binding affinity for CO 2 . Computational analyses further support these dynamic observations. The beneficial role of these structural dynamics could play an essential role in building a deeper understanding of CO 2 binding in MOFs.

Elucidating the Competitive Adsorption of H2O and CO2 in CALF-20: New Insights for Enhanced Carbon Capture Metal–Organic Frameworks

“…The MB-pol − and MB-nrg , data-driven many-body PEFs were used to model the H 2 O and CO 2 molecules, respectively. Previous studies have demonstrated that these PEFs are transferable across the different phases of pure H 2 O − , and CO 2 , , able to reproduce the properties of H 2 O and CO 2 mixtures, and accurately predict the behavior of H 2 O ,, and CO 2 molecules in MOFs.…”

Modulator-Dependent Dynamics Synergistically Enabled Record SO2 Uptake in Zr(IV) Metal–Organic Frameworks Based on Pyrene-Cored Molecular Quadripod Ligand

“…Note that such type V isotherms for SO 2 sorption have been computationally predicted in other MOF materials with simple nonfunctionalized linkers and exceptionally high pore volumes such as MOF-177 and IRMOF series, , which apparently is not the case for Zr-TPA-FA and Zr-TPA-HAc. Inspired by our recent work that discovered the unexpected modulator–CO 2 dynamics in Zr-MOFs both experimentally and computationally, which unveil the important role of the capping modulator in enhancing CO 2 binding within the pores, we hypothesize that the lability differences of the capping modulator could also remarkably influence the SO 2 sorption performances of Zr-TPA variants through distinct modulator–node dynamics (Figure a). Therefore, we performed density functional theory (DFT) calculations on cluster models of the two representative MOFs of Zr-TPA-FA and Zr-TPA-TFA to assess the preferential physical and chemical binding sites of SO 2 and probe the experimentally observed modulator effects on sorption (computational details in Supporting Information).…”

Emerging porous materials for carbon dioxide adsorptive capture: progress and challenges

“…Defect engineering, originating from missing building blocks in the framework, is considered an efficient solution to provide more coordinatively unsaturated sites, thus improving CO 2 separation performance. 32,33 One interesting example is MOF-808, 34 a typical zirconium-based MOF, which allows for easy access to open zirconium sites due to minimized steric inhibition. It exhibited special dynamic behaviour in the pores of variants of MOF-808-X with different capping modulators (formate, acetate, and trifluoroacetate, termed FA, AA, and TFA), affording open zirconium sites for direct chemisorption of CO 2 .…”