Water-stable metal–organic frameworks (MOFs): rational construction and carbon dioxide capture

Abstract

Metal-organic frameworks (MOFs) are considered to be a promising porous material due to their excellent porosity and chemical tailorability. However, due to the relatively weak strength of coordination bonds, the...

Metal–Organic Framework Stability in Water and Harsh Environments from Data-Driven Models Trained on the Diverse WS24 Data Set

“…However, the presence and identity of counterions can play a role in MOF water stability, ,, so consideration of guest molecules could improve the models in the future. Furthermore, WS24 and the models in this study cover pristine MOFs, and thus the models are not applicable to MOFs that have undergone postsynthetic modifications like hydrophobic coatings, introduction of guest molecules, and incorporation into composite materials that have been shown to improve water stability. ,,,,− The current approach employs crystal structures determined by X-ray diffraction, which captures the average structure of a MOF and thus does not provide information on defects at low defect concentration . However, defects in MOFs worsen water stability, so a fuller understanding of the concentration of defects could improve future models.…”

“…Several heuristics for assessing the water stability of MOFs have been proposed, informed by examples of experimentally realized MOFs with varying levels of water stability. − ,,− Exemplary of these heuristics is a proposal to strengthen the metal–linker bond by selecting stronger bonding metal–linker combinations such as Zr 4+ with carboxylate linkers, an approach that has proven to be effective. ,, Such combinations can be selected using Pearson’s hard–soft acid–base (HSAB) theory, whereby, high-valent, hard metals are expected to form strong bonds with hard bases, e.g., Zr 4+ with oxygen-coordinating carboxylate linkers, while lower-valent, softer metals are expected to form strong bonds with soft base linkers, e.g., Co 2+ with nitrogen-coordinating azolate linkers. ,,− Nevertheless, there are exceptions to this rule, such as the water-stable MOF PIZA-1, which contains Co­(II) nodes and carboxylate-coordinating linkers. , Another commonly used heuristic is that metal nodes with many connection points to linkers lead to water-stable MOFs, as their high coordination numbers both sterically prevent water from approaching the metal–linker bond and lead to a kinetic barrier to water-mediated degradation as multiple bonds need to be disrupted prior to framework collapse. − ,,, Even so, there exist numerous examples of water-stable MOFs with low coordination SBUs, − indicating that a high number of linker connection points is not strictly required. Thus, heuristics developed based on the strength and number of metal–linker bonds in MOFs cannot reliably predict MOF water stability.…”

“…Thus, heuristics developed based on the strength and number of metal–linker bonds in MOFs cannot reliably predict MOF water stability. Other heuristic strategies have been applied, such as steric protection and hydrophobicity of the metal–linker bond, − ,,− , use of short, rigid linkers, ,,,,, or framework interpenetration, ,,,,, but numerous water-stable MOFs have been noted that violate each of these cases (e.g., low hydrophobicity, longer linkers − ). Overall, while these heuristics have great utility and are based on physical principles, they are also simplifications and consequently have numerous exceptions.…”

Ni–Co alloys via controlled pyrolysis of NiCo–MOF as heterogeneous hydrogenation catalysts

“…Metal–organic frameworks (MOFs) have extensive applications in gas storage/separation, drug delivery, chemical sensing, and catalysis science due to their high surface area, structural diversity and unique thermal behavior. 1–3 The involvement of metal nanoparticles (MNPs) in MOFs can further upgrade their performances by the synergistic effect between MNPs and MOFs. For example, H.-L. Jiang et al 4 encapsulated electronic-rich PdCu nanoparticles into sulfonate functionalized metal–organic frameworks, and further regulated the microenvironment by coating the hydrophobic polydimethylsiloxane layer.…”

Systemic regulation of binding sites in porous coordination polymers for ethylene purification from ternary C2 hydrocarbons

“…However, from an energy point of view, it is crucial to remove both by-products in one-step with an adsorbent, but the challenge is enormous. 23–25…”