# Flexible and defective MOFs

> MOF flexibility and defects on one page: MIL-53 breathing between large and narrow pores with water, the imidazolate linker swing that opens ZIF-8, the sudden pore contraction of DUT-49 that pushes methane out, missing-linker and missing-cluster defects in UiO-66, correlated missing clusters in reo nano-regions, and what caps the freed sites. Every statement and number is quoted from the cited papers.

- Page: https://www.labcanvas.com/templates/mof-guides/flexible-defective-mofs
- Open in the LabCanvas editor (LabCanvas account): https://www.labcanvas.com/editor.html?template=mof-flexibility-defects
- Updated: 2026-10-14
- Category: MOF guides
- Method: Flexibility and defects
- Product: Flexible frameworks (MIL-53, ZIF-8, DUT-49) and defective UiO-66
- Key result: Frameworks, clusters and defects drawn by LabCanvas from the cited structures; the numbers of defects drawn are schematic, and no panel is an isotherm or a diffraction pattern
- Figure: 1920 × 1080 px, 45 editable layers (6 generated objects with settings)

## Steps

1. **Breathing MIL-53**: MIL-53(Cr): chains of Cr(III) octahedra linked by terephthalate; water clips the pores, which reopen when the channels empty, a breathing of more than 5 Å (Serre 2002). MIL-53(Cr) adopts a narrow- or a large-pore form depending on the water loading (Haigis 2013). In MIL-53(Al), water H-bonded to the carboxylates contracts the rhombic tunnels, leaving the bridging OH untouched (Loiseau 2004). Soft porous crystals respond to guests, light or electric fields yet stay crystalline, changing their channels reversibly (Horike 2009)
2. **Linker swing in ZIF-8**: ZIF-8 has large cavities joined by narrow windows; gas uptake changes its structure as a very high pressure (14,700 bar) does, by a swing of the imidazolate linkers that opens access to the pores (Fairen-Jimenez 2011). Heat-capacity data of the CO₂-loaded solid point to a gate-opening transition (Rosen 2020). Breathing and swelling of flexible MOFs are phase transitions set off by guest adsorption or desorption, light, heat or mechanical stimuli (Schneemann 2014)
3. **DUT-49 contracts**: DUT-49 desorbs methane or n-butane as the pressure rises, in a set temperature and pressure range: a sudden, hysteretic contraction of the pores releases the guests (Krause 2016). Its biphenyl link buckles as the framework contracts while the metal–organic polyhedra stay unchanged, and the methane released comes mainly from the largest (octahedral) pores (Krause 2019). Other kinds: MIL-88 swells reversibly, its cell volume nearly doubling (~85%) with its topology kept (Mellot-Draznieks 2005; Serre 2007); Co(bdp) turns from a collapsed into expanded phases as the gas pressure rises (Taylor 2016)
4. **Missing linkers, clusters**: Missing-linker and missing-node defects raise the number of active sites and ease diffusion, improving catalysis, and can add properties the parent MOF lacks, such as electronic conductivity (Dissegna 2018). Neutron diffraction found ~10% of UiO-66’s linkers missing, its connection falling from 12 to ~11; acetic acid modulator and synthesis time tune the vacancies, giving pore volumes of 0.44–1.0 cm³/g and BET areas of 1000–1600 m²/g (Wu 2013). In a missing-cluster defect the Zr₆ node is gone with all twelve of its linkers (Islamov 2023)
5. **Correlated missing clusters**: In UiO-66(Hf) made with formic acid, missing clusters are correlated: about half the clusters lie in or next to nano-regions where the cell-corner clusters are absent, dispersed in the 12-connected framework, and longer reaction times grow the regions; they are a MOF analogue of correlated Schottky vacancies in rock-salt transition-metal monoxides (Cliffe 2014). These nano-regions have reo topology, the clusters 8-connected instead of 12-connected, a quarter of the clusters absent (Islamov 2023)
6. **What caps the sites**: Single-crystal diffraction of UiO-66 showed water bound directly to the Zr at missing-linker sites, with hydroxide hydrogen-bonded in the pores balancing the charge (Trickett 2015). Missing-linker and missing-cluster sites are terminated with formate, as experiments suggest (Islamov 2023); in UiO-66(Hf) made with formic acid, the sites left by missing clusters are expected to hold formate (Cliffe 2014). In UiO-66(Zr) made with trifluoroacetic acid and HCl, thermal activation removes the trifluoroacetate that had replaced some terephthalates, leaving many open sites (Vermoortele 2013)

## Strengths

- A sharp phase change at a set CH₄ pressure raises the usable capacity and cuts the heat released (Mason 2015)
- Defects raise the number of active sites and ease diffusion (Dissegna 2018)
- Removing trifluoroacetate from UiO-66 gave a highly active Lewis-acid catalyst (Vermoortele 2013)

## Limitations

- Defects lower thermal stability and water resistance (Islamov 2023)
- DUT-49’s contraction is sudden and hysteretic, in a set temperature and pressure range (Krause 2016)
- Longer reaction times grow the missing-cluster regions of UiO-66(Hf) (Cliffe 2014)

## References

1. Serre et al., “Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr^III(OH)·{O₂C–C₆H₄–CO₂}·{HO₂C–C₆H₄–CO₂H}ₓ·H₂Oᵧ”, J. Am. Chem. Soc. 2002. https://doi.org/10.1021/ja0276974 (primary)
2. Haigis et al., “Investigation of structure and dynamics of the hydrated metal-organic framework MIL-53(Cr) using first-principles molecular dynamics”, Phys. Chem. Chem. Phys. 2013. https://doi.org/10.1039/c3cp53126k (primary)
3. Loiseau et al., “A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration”, Chem. Eur. J. 2004. https://doi.org/10.1002/chem.200305413 (primary)
4. Horike, Shimomura & Kitagawa, “Soft porous crystals”, Nat. Chem. 2009. https://doi.org/10.1038/nchem.444 (primary)
5. Fairen-Jimenez et al., “Opening the gate: framework flexibility in ZIF-8 explored by experiments and simulations”, J. Am. Chem. Soc. 2011. https://doi.org/10.1021/ja202154j (primary)
6. Rosen et al., “Thermodynamic evidence of structural transformations in CO₂-loaded metal-organic framework Zn(MeIm)₂ from heat capacity measurements”, J. Am. Chem. Soc. 2020. https://doi.org/10.1021/jacs.9b13883 (primary)
7. Schneemann et al., “Flexible metal-organic frameworks”, Chem. Soc. Rev. 2014. https://doi.org/10.1039/c4cs00101j (primary)
8. Krause et al., “A pressure-amplifying framework material with negative gas adsorption transitions”, Nature 2016. https://doi.org/10.1038/nature17430 (primary)
9. Krause et al., “Towards general network architecture design criteria for negative gas adsorption transitions in ultraporous frameworks”, Nat. Commun. 2019. https://doi.org/10.1038/s41467-019-11565-3 (primary)
10. Mellot-Draznieks et al., “Very large swelling in hybrid frameworks: a combined computational and powder diffraction study”, J. Am. Chem. Soc. 2005. https://doi.org/10.1021/ja054900x (primary)
11. Serre et al., “Role of solvent-host interactions that lead to very large swelling of hybrid frameworks”, Science 2007. https://doi.org/10.1126/science.1137975 (primary)
12. Taylor et al., “Tuning the adsorption-induced phase change in the flexible metal-organic framework Co(bdp)”, J. Am. Chem. Soc. 2016. https://doi.org/10.1021/jacs.6b09155 (primary)
13. Mason et al., “Methane storage in flexible metal-organic frameworks with intrinsic thermal management”, Nature 2015. https://doi.org/10.1038/nature15732 (primary)
14. Dissegna et al., “Defective metal-organic frameworks”, Adv. Mater. 2018. https://doi.org/10.1002/adma.201704501 (primary)
15. Wu et al., “Unusual and highly tunable missing-linker defects in zirconium metal-organic framework UiO-66 and their important effects on gas adsorption”, J. Am. Chem. Soc. 2013. https://doi.org/10.1021/ja404514r (primary)
16. Islamov et al., “Correlated missing linker defects increase thermal conductivity in metal-organic framework UiO-66”, Chem. Sci. 2023. https://doi.org/10.1039/d2sc06120a (primary)
17. Cliffe et al., “Correlated defect nanoregions in a metal-organic framework”, Nat. Commun. 2014. https://doi.org/10.1038/ncomms5176 (primary)
18. Trickett et al., “Definitive molecular level characterization of defects in UiO-66 crystals”, Angew. Chem. Int. Ed. 2015. https://doi.org/10.1002/anie.201505461 (primary)
19. Vermoortele et al., “Synthesis modulation as a tool to increase the catalytic activity of metal-organic frameworks: the unique case of UiO-66(Zr)”, J. Am. Chem. Soc. 2013. https://doi.org/10.1021/ja405078u (primary)

Credit: Drawn by LabCanvas after Serre et al., J. Am. Chem. Soc. 2002 (doi:10.1021/ja0276974), Fairen-Jimenez et al., J. Am. Chem. Soc. 2011, Krause et al., Nature 2016 and Horike, Shimomura & Kitagawa, Nat. Chem. 2009, and the papers in the details.

## Questions

**What does the “Flexible and defective MOFs” template show?** MOF flexibility and defects on one page: MIL-53 breathing between large and narrow pores with water, the imidazolate linker swing that opens ZIF-8, the sudden pore contraction of DUT-49 that pushes methane out, missing-linker and missing-cluster defects in UiO-66, correlated missing clusters in reo nano-regions, and what caps the freed sites. Every statement and number is quoted from the cited papers.

**What are the steps shown in “Flexible and defective MOFs”?** 1. Breathing MIL-53: MIL-53(Cr): chains of Cr(III) octahedra linked by terephthalate; water clips the pores, which reopen when the channels empty, a breathing of more than 5 Å (Serre 2002). MIL-53(Cr) adopts a narrow- or a large-pore form depending on the water loading (Haigis 2013). In MIL-53(Al), water H-bonded to the carboxylates contracts the rhombic tunnels, leaving the bridging OH untouched (Loiseau 2004). Soft porous crystals respond to guests, light or electric fields yet stay crystalline, changing their channels reversibly (Horike 2009). 2. Linker swing in ZIF-8: ZIF-8 has large cavities joined by narrow windows; gas uptake changes its structure as a very high pressure (14,700 bar) does, by a swing of the imidazolate linkers that opens access to the pores (Fairen-Jimenez 2011). Heat-capacity data of the CO₂-loaded solid point to a gate-opening transition (Rosen 2020). Breathing and swelling of flexible MOFs are phase transitions set off by guest adsorption or desorption, light, heat or mechanical stimuli (Schneemann 2014). 3. DUT-49 contracts: DUT-49 desorbs methane or n-butane as the pressure rises, in a set temperature and pressure range: a sudden, hysteretic contraction of the pores releases the guests (Krause 2016). Its biphenyl link buckles as the framework contracts while the metal–organic polyhedra stay unchanged, and the methane released comes mainly from the largest (octahedral) pores (Krause 2019). Other kinds: MIL-88 swells reversibly, its cell volume nearly doubling (~85%) with its topology kept (Mellot-Draznieks 2005; Serre 2007); Co(bdp) turns from a collapsed into expanded phases as the gas pressure rises (Taylor 2016). 4. Missing linkers, clusters: Missing-linker and missing-node defects raise the number of active sites and ease diffusion, improving catalysis, and can add properties the parent MOF lacks, such as electronic conductivity (Dissegna 2018). Neutron diffraction found ~10% of UiO-66’s linkers missing, its connection falling from 12 to ~11; acetic acid modulator and synthesis time tune the vacancies, giving pore volumes of 0.44–1.0 cm³/g and BET areas of 1000–1600 m²/g (Wu 2013). In a missing-cluster defect the Zr₆ node is gone with all twelve of its linkers (Islamov 2023). 5. Correlated missing clusters: In UiO-66(Hf) made with formic acid, missing clusters are correlated: about half the clusters lie in or next to nano-regions where the cell-corner clusters are absent, dispersed in the 12-connected framework, and longer reaction times grow the regions; they are a MOF analogue of correlated Schottky vacancies in rock-salt transition-metal monoxides (Cliffe 2014). These nano-regions have reo topology, the clusters 8-connected instead of 12-connected, a quarter of the clusters absent (Islamov 2023). 6. What caps the sites: Single-crystal diffraction of UiO-66 showed water bound directly to the Zr at missing-linker sites, with hydroxide hydrogen-bonded in the pores balancing the charge (Trickett 2015). Missing-linker and missing-cluster sites are terminated with formate, as experiments suggest (Islamov 2023); in UiO-66(Hf) made with formic acid, the sites left by missing clusters are expected to hold formate (Cliffe 2014). In UiO-66(Zr) made with trifluoroacetic acid and HCl, thermal activation removes the trifluoroacetate that had replaced some terephthalates, leaving many open sites (Vermoortele 2013).

**Which papers is “Flexible and defective MOFs” based on?** Serre et al., “Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr^III(OH)·{O₂C–C₆H₄–CO₂}·{HO₂C–C₆H₄–CO₂H}ₓ·H₂Oᵧ”, J. Am. Chem. Soc. 2002 (doi:10.1021/ja0276974); Haigis et al., “Investigation of structure and dynamics of the hydrated metal-organic framework MIL-53(Cr) using first-principles molecular dynamics”, Phys. Chem. Chem. Phys. 2013 (doi:10.1039/c3cp53126k); Loiseau et al., “A rationale for the large breathing of the porous aluminum terephthalate (MIL-53) upon hydration”, Chem. Eur. J. 2004 (doi:10.1002/chem.200305413); Horike, Shimomura & Kitagawa, “Soft porous crystals”, Nat. Chem. 2009 (doi:10.1038/nchem.444); Fairen-Jimenez et al., “Opening the gate: framework flexibility in ZIF-8 explored by experiments and simulations”, J. Am. Chem. Soc. 2011 (doi:10.1021/ja202154j); Rosen et al., “Thermodynamic evidence of structural transformations in CO₂-loaded metal-organic framework Zn(MeIm)₂ from heat capacity measurements”, J. Am. Chem. Soc. 2020 (doi:10.1021/jacs.9b13883); Schneemann et al., “Flexible metal-organic frameworks”, Chem. Soc. Rev. 2014 (doi:10.1039/c4cs00101j); Krause et al., “A pressure-amplifying framework material with negative gas adsorption transitions”, Nature 2016 (doi:10.1038/nature17430); Krause et al., “Towards general network architecture design criteria for negative gas adsorption transitions in ultraporous frameworks”, Nat. Commun. 2019 (doi:10.1038/s41467-019-11565-3); Mellot-Draznieks et al., “Very large swelling in hybrid frameworks: a combined computational and powder diffraction study”, J. Am. Chem. Soc. 2005 (doi:10.1021/ja054900x); Serre et al., “Role of solvent-host interactions that lead to very large swelling of hybrid frameworks”, Science 2007 (doi:10.1126/science.1137975); Taylor et al., “Tuning the adsorption-induced phase change in the flexible metal-organic framework Co(bdp)”, J. Am. Chem. Soc. 2016 (doi:10.1021/jacs.6b09155); Mason et al., “Methane storage in flexible metal-organic frameworks with intrinsic thermal management”, Nature 2015 (doi:10.1038/nature15732); Dissegna et al., “Defective metal-organic frameworks”, Adv. Mater. 2018 (doi:10.1002/adma.201704501); Wu et al., “Unusual and highly tunable missing-linker defects in zirconium metal-organic framework UiO-66 and their important effects on gas adsorption”, J. Am. Chem. Soc. 2013 (doi:10.1021/ja404514r); Islamov et al., “Correlated missing linker defects increase thermal conductivity in metal-organic framework UiO-66”, Chem. Sci. 2023 (doi:10.1039/d2sc06120a); Cliffe et al., “Correlated defect nanoregions in a metal-organic framework”, Nat. Commun. 2014 (doi:10.1038/ncomms5176); Trickett et al., “Definitive molecular level characterization of defects in UiO-66 crystals”, Angew. Chem. Int. Ed. 2015 (doi:10.1002/anie.201505461); Vermoortele et al., “Synthesis modulation as a tool to increase the catalytic activity of metal-organic frameworks: the unique case of UiO-66(Zr)”, J. Am. Chem. Soc. 2013 (doi:10.1021/ja405078u).

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