Computational chemistry
Defect hydroxides in UiO-66 shuttle protons
Open access · cc by · source: Europe PMC
Simulations of missing-linker UiO-66 put charge-balancing OH on under-coordinated Zr and show those sites swap between hydroxide and water by rapid proton transfer with extra-framework water.
Study at a glance
- Design
- Computational / modelling — PBE0+D3 and AIMD of defective UiO-66 proton transfer and NH3 binding
- N
- Periodic DFT/AIMD study of MOF defects — no sample N
- Population
- Defective UiO-66 zirconium MOF models
- Outcome
- Dynamic Brønsted acidity and proton-transfer barriers at defect sites
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Average Zr⋯O = 2.23 Å matches 300 K experiment. Direct O0–O1 proton transfer barrier is only 6.5 kJ mol−1 versus 27.5 for an O3-mediated path. NH3 binds 110.1 vs 75.8 kJ mol−1 at defect vs perfect regions. Water can leave, exposing frustrated Lewis pair-like Zr sites.
Methodology
Authors ran PBE0+D3 static optimisations and AIMD at 100–700 K on defective UiO-66, compared Zr–O distances to diffraction, estimated proton-transfer barriers, and used NH3 binding as a Brønsted-acidity probe.
Limitations
The dynamics are computed; they are invisible to time-averaged XRD and are not a measured catalytic turnover of a substrate.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
AIMD of defective UiO-66 makes a proton shuttle that diffraction cannot see. Average Zr⋯O = 2.23 Å matches 300 K experiment, but a direct O0–O1 proton-transfer barrier is only 6.5 kJ mol⁻¹ versus 27.5 kJ mol⁻¹ for an O3-mediated path. NH₃ binds 110.1 versus 75.8 kJ mol⁻¹ at defect versus perfect regions; water can leave, exposing frustrated-Lewis-pair-like Zr. The dynamics are computed, not a measured catalytic turnover.
Evidence for the claim as stated.
MD that is later tested in a cuvette is not the same deliverable as MD that stays inside the computer. Mpro peptides have micromolar IC₅₀ values; GFP AIMD proton-transfer times disagree with 3/10 ps FSRS phases; UiO-66 proton hops are invisible to time-averaged XRD. A student who says 'MD showed the mechanism' must say whether a wet observable confirmed it.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
MD that is later tested in a cuvette is not the same deliverable as MD that stays inside the computer. Mpro peptides have micromolar IC₅₀ values; GFP AIMD proton-transfer times disagree with 3/10 ps FSRS phases; UiO-66 proton hops are invisible to time-averaged XRD. A student who says 'MD showed the mechanism' must say whether a wet observable confirmed it.
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Same topic cluster — not a recommendation engine.