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Disclosing the Complex Structure of UiO-66 Metal Organic Framework: A Synergic Combination of Experiment and Theory
Summary:
The authors from the University of Turin and the University of Oslo developed a comprehensive structural model for UiO-66 (Zr-BDC MOF) through a synergic combination of XRPD, EXAFS, IR, UV–vis, and periodic DFT. They accurately described its hydroxylated and dehydroxylated forms, revealing reversible dehydration/hydration, high thermal stability up to 375 °C, and resistance to water, acids and bases, providing reliable foundations for catalysis and gas-separation applications.
Background:
1. To address the difficulty of refining complex MOF structures solely from powder diffraction data, prior studies often failed to capture subtle local distortions and missed linker vacancies.
2. The authors proposed an iterative XRPD/EXAFS/ab-initio workflow and quantitatively resolved the distortion of Zr₆O₆ clusters upon dehydroxylation, also estimating the intrinsic defectivity (~11 BDC per Zr₆ cluster).
Research Content:
1. Synthesis:
UiO-66 was synthesized solvothermally from ZrCl₄ and 1,4-benzenedicarboxylic acid in DMF/H₂O at 120 °C for 24 h.
2. Characterizations:
1) BET: 1069 m² g⁻¹ type-I microporous isotherm; 2) SEM: 1–2 µm inter-grown cubic crystals;
3) In-situ XRPD, TGA/MS, EXAFS, IR and UV–vis together with periodic B3LYP calculations tracked reversible μ₃–OH removal and Zr-coordination change (8 → 7).
3. Application:
The material maintained crystallinity after 24 h in water, acetone, ethanol, benzene, DMF, 2 M HCl or 2 M NaOH, and after heating to 375 °C, proving suitability for harsh-condition catalysis/adsorption.
4. Mechanism:
μ₃–OH loss triggers an axial compression of the Zr₆ octahedron (Td→D₃d), splitting Zr–Zr distances; DFT shows π–π* dominated band gap (4.07–4.56 eV) tuned by linker states, while electrostatic potential maps indicate preferential adsorption on BDC linkers.
Outlook:
This work establishes the first fully validated multi-technique structure of UiO-66, demonstrates the importance of combining long-range and local probes for defect-rich MOFs, and sets a benchmark for extending the approach to functionalized UiO-67/68 analogues.
Disclosing the Complex Structure of UiO-66 Metal Organic Framework: A Synergic Combination of Experiment and Theory
Authors: Loredana Valenzano, Bartolomeo Civalleri, Sachin Chavan, Silvia Bordiga, Merete H. Nilsen, Søren Jakobsen, Karl Petter Lillerud, Carlo Lamberti
DOI: 10.1021/cm1022882
Link: https://pubs.acs.org/doi/10.1021/cm1022882
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