Dynamic acidity in defective UiO-66

Ling, Sanliang; Slater, Ben

doi:10.1039/c5sc04953a

Cited by 158 publications

(182 citation statements)

References 47 publications

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“…46,47 In this work, we have used one of the most popular pairwise additive descriptions of the dispersion interactions as developed by Grimme et al, i.e., the D3 method 48 with the Axilrod–Teller–Muto three-body terms, in combination with the conventional PBE and PBE0 functionals. The same method was used in our previous work on MIL-53, 49,50 UiO-66, 51 and MOF-74 24 types of MOFs, and we achieved very good agreement between theory and experimental results on structures and calorimetric measurements. We note that a hybrid functional is necessary here to provide a correct description of the electronic structures and host–guest interactions of MOF-74 materials featuring M 2+ cations with unpaired electrons, including Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ , and Cu 2+ .…”

Section: Methodssupporting

confidence: 72%

Rational Design of a Low-Cost, High-Performance Metal–Organic Framework for Hydrogen Storage and Carbon Capture

et al. 2017

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We present the in silico design of a MOF-74 analogue, hereon known as M2(DHFUMA) [M = Mg, Fe, Co, Ni, Zn], with enhanced small-molecule adsorption properties over the original M2(DOBDC) series. Constructed from 2,3-dihydroxyfumarate (DHFUMA), an aliphatic ligand which is smaller than the aromatic 2,5-dioxidobenzene-1,4-dicarboxylate (DOBDC), the M2(DHFUMA) framework has a reduced channel diameter, resulting in higher volumetric density of open metal sites and significantly improved volumetric hydrogen (H2) storage potential. Furthermore, the reduced distance between two adjacent open metal sites in the pore channel leads to a CO2 binding mode of one molecule per two adjacent metals with markedly stronger binding energetics. Through dispersion-corrected density functional theory (DFT) calculations of guest–framework interactions and classical simulation of the adsorption behavior of binary CO2:H2O mixtures, we theoretically predict the M2(DHFUMA) series as an improved alternative for carbon capture over the M2(DOBDC) series when adsorbing from wet flue gas streams. The improved CO2 uptake and humidity tolerance in our simulations is tunable based upon metal selection and adsorption temperature which, combined with the significantly reduced ligand expense, elevates this material’s potential for CO2 capture and H2 storage. The dynamical and elastic stabilities of Mg2(DHFUMA) were verified by hybrid DFT calculations, demonstrating its significant potential for experimental synthesis.

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Section: Methodssupporting

confidence: 72%

Rational Design of a Low-Cost, High-Performance Metal–Organic Framework for Hydrogen Storage and Carbon Capture

et al. 2017

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“…The proton migration likely occurs via trapped alcohol in the MOF pores and through mobility of the H + from the clusters’ bridging hydroxides, a process very similar to that observed in Zr-based MOFs. 32,33 The H + ion accompanying the e − will likely bind to a bridging oxygen on the MIL-125 cluster to form a hydroxide. A similar mechanism has been shown for COK-69, another photoreducible Ti-MOF.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Bulk-to-Surface Proton-Coupled Electron Transfer Reactivity of the Metal–Organic Framework MIL-125

et al. 2018

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Stoichiometric proton-coupled electron transfer (PCET) reactions of the metal−organic framework (MOF) MIL-125, Ti8O8(OH)4(bdc)6 (bdc = terephthalate), are described. In the presence of UV light and 2-propanol, MIL-125 was photoreduced to a maximum of 2(e−/H+) per Ti8 node. This stoichiometry was shown by subsequent titration of the photoreduced material with the 2,4,6-tri-tert-butylphenoxyl radical. This reaction occurred by PCET to give the corresponding phenol and the original, oxidized MOF. The high level of charging, and the independence of charging amount with particle size of the MOF samples, shows that the MOF was photocharged throughout the bulk and not only at the surface. NMR studies showed that the product phenol is too large to fit in the pores, so the phenoxyl reaction must have occurred at the surface. Attempts to oxidize photoreduced MIL-125 with pure electron acceptors resulted in multiple products, underscoring the importance of removing e− and H+ together. Our results require that the e− and H+ stored within the MOF architecture must both be mobile to transfer to the surface for reaction. Analogous studies on the soluble cluster Ti8O8(OOCtBu)16 support the notion that reduction occurs at the Ti8 MOF nodes and furthermore that this reduction occurs via e−/H+ (H-atom) equivalents. The soluble cluster also suggests degradation pathways for the MOFs under extended irradiation. The methods described are a facile characterization technique to study redox-active materials and should be broadly applicable to, for example, porous materials like MOFs.

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“…[26] It was observed that both activated and unactivated samples exhibited 96 % conversion of benzaldehyde at 40°C. [28,29] UiO-66 and UiO-67 were tested as heterogeneous solid catalysts for the acetalization of benzaldehyde with methanol. These results clearly indicate that the presence of acetic acid during UiO-66 synthesis enhances the catalytic performance of UiO-66.…”

Section: Nodes As Lewis Acidsmentioning

confidence: 99%

Engineering UiO‐66 Metal Organic Framework for Heterogeneous Catalysis

et al. 2019

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frameworks (MOFs) are currently attracting considerable attention as heterogeneous catalysts at moderate temperatures, mainly for liquid-phase reactions. Since structural stability is one of the major concerns for the use of MOFs in catalysis, particularly considering that frequently some of the reported MOF materials are very unstable, the interest in this area has been focused on those MOFs exhibiting the highest structural robustness, UiO-66 being among the most widely used. Two introductory sections deal with the synthesis, structure and main properties of UiO-66, including its remarkable thermal (up to 350°C) and chemical (aqueous solution in a wide pH range) stability. The main body of the review summarizes those examples of using UiO-66 in catalysis grouped according to the nature of the active sites, starting with the use of UiO-66 as Lewis acids. In this section, emphasis has been made in the recent strategies to create structural defects in a controlled way that generate Lewis acidity. Other sections cover examples illustrating substituted terephthalate as active sites and the evidence that there is a synergy between acid and basic sites in close proximity that make some of these UiO-66 with substituents at the linker to act as dual acid-base catalysts. Other sections are focused on the use of UiO-66 as hosts of metal nanoparticles, metal oxides and other host, remarking the influence that the nature of UiO-66 and the possible presence of substituents in the framework play on the activity of the incorporated guest. The last section summarizes the current state of the art in the use of UiO-66 in catalysis and provides our views on future developments regarding the application of UiO-66 in industrial processes.

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Dynamic acidity in defective UiO-66

Cited by 158 publications

References 47 publications

Rational Design of a Low-Cost, High-Performance Metal–Organic Framework for Hydrogen Storage and Carbon Capture

Rational Design of a Low-Cost, High-Performance Metal–Organic Framework for Hydrogen Storage and Carbon Capture

Bulk-to-Surface Proton-Coupled Electron Transfer Reactivity of the Metal–Organic Framework MIL-125

Engineering UiO‐66 Metal Organic Framework for Heterogeneous Catalysis

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