Table 1 Selected seminal works on defect engineering in MOFs
From: Benefits and complexity of defects in metal-organic frameworks
Notes on methodology | Defect type and implicationsa | MOF(s) | Year | Ref. |
|---|---|---|---|---|
UiO Series | ||||
Solvothermal synthesis (intrinsic defectivity) | Missing linker | UiO-66 | 2011 | |
Solvothermal, modulator and reaction time varied | Missing linker defects tuned by varying modulator/reaction time | UiO-66 | 2013 | |
Solvothermal, modulated synthesis | Correlated missing cluster defects | UiO-66(Hf) | 2014 | |
High linker/SBU ratio and high synthesis temperature | Minimal defectivity | UiO-66 | 2014 | |
Acid modulation in solvothermal synthesis | Missing linker in each Zr6 node | UiO-67 | 2015 | |
Solvothermal, modulated synthesis | Predominantly missing cluster defects | UiO-66 | 2016 | |
Post-synthetic thermal decomposition of doped thermolabile linker | Missing linker defects | UiO-66 mixed linker | 2017 | |
Modulated synthesis with trifluoroacetic acid followed by heat treatment | Trifluoracetic acid coordinated at missing linker defects can be removed by heating at 320 °C under vacuum to enhance mesopore size, or retained if heated at 200 °C. | UiO-66 | 2017 | |
Synthesis at temperatures from 25–130 °C | Increasing synthesis temperature results in reduced defectivity | UiO-66-X (X = NH2, OH, NO2) | 2017 | |
Solvothermal synthesis using formic, acetic and benzoic acid modulators | Formic acid observed to form pore blockage defects, benzoic acid generates cluster defects/microporosity and acetic acid was associated with missing linker defects | UiO-AZB | 2017 | |
Solvothermal synthesis using excess modulator and sub-stoichiometric linker. | Hierarchical porosity produced by missing linkers/clusters | UiO-66, MOF-808, MIL-53, DUT-5 | 2017 | |
Post-synthetic healing of missing linker defects | Missing linker defects healed by post-synthetic treatment with solution containing excess linker. Improved sieving capacity observed. | UiO-66-(OH)2 | 2017 | |
Solvothermal synthesis using acid modulator | Missing linker defects, detrimental towards butane isomer separation | MOF-801 | 2018 | |
Solvothermal synthesis, post-synthetic heat treatment | IR spectroscopy used to monitor highly sensitive CO probe molecules in UiO-66, revealing missing linker defects (coordinatively unsaturated ZrIV sites) and evolution of defect landscape during post-synthetic heat treatment of MOF. | UIO-66 | 2018 | |
Solvothermal synthesis using acid modulator | Defects found to be detrimental towards C3 hydrocarbon sieving properties. | MOF-801 | 2019 | |
Acid modulation in solvothermal synthesis | Ordered missing linker and missing cluster defects | UiO-66 | 2019 | |
Post-synthetic defect healing | Missing linker defects healed by post-synthetic reaction with solution containing excess linker. Samples with reduced defectivity exhibit enhanced Kr/Xe selectivity. | NU-403 | 2020 | |
Modulator free solvothermal synthesis, water conc. controlled | Predominantly missing cluster defects | UiO-66 | 2020 | |
Solvothermal synthesis using 4-sulfonatobenzoate as both modulator to generate defects and hemilabile structural linker. H2SO4 post-synthetic treatment increases missing linker defectivity. | Up to six missing linkers per cluster. Increased thermal stability observed in defective structure due to hemilabile linker. | UiO-66 | 2020 | |
Acid modulated solvothermal synthesis, varied linker/SBU ratio | Direct imaging of correlated defects with scanning electron diffraction | UiO-66(Hf) | 2020 | |
Targeted removal of Zn clusters via acid wash, Zr-oxo clusters intact | Missing cluster defects | UiO-66(Zn,Zr) | 2021 | |
Solvothermal synthesis temperature used to tune defectivity | Tuning hydrophobicity via defectivity | UiO-66 | 2022 | |
Solvothermal synthesis using mixed linker approach which includes the thermolabile adipic acid linker. | Missing linker defects generated during thermolysis of adipic acid linkers at 300 °C. | UiO-66 | 2022 | |
Solvothermal, modulators (p-nitrobenzoic acid or p-hydroxybenzoic acid) act as defective linkers. | Missing linker defects arising from incorporation of modulators in structure. | UiO-66 | 2022 | |
Solvothermal, 80 °C, 15-fold ligand/SBU ratio | Minimal defectivity | UiO-66 | 2023 | |
Structural evolution under electron beam | Missing linker defects | UiO-66 | 2023 | |
Solvothermal synthesis, varied linker and modulator concentration | Controlled correlated missing linker and cluster defects | UiO-66 | 2023 | |
Acid modulated solvothermal synthesis | Missing linker defects promote longer lifetime excited states for catalysis | UiO type framework | 2024 | |
Cluster-cluster co-nucleation (CCCN) strategy | Well-defined cluster defects | UiO-66 | 2024 | |
Reaction-diffusion process at room temperature | Missing linkers | UiO-66(OH)2 | 2024 | |
Acetic acid modulated reaction diluted using ethanol to promote ultrasmall nanocrystals (4–6 nm) | Highly defective nanocrystals, up to 45% missing linkers | UiO- and MOF-801 frameworks | 2024 | |
HKUST Series | ||||
Solvothermal synthesis (intrinsic defectivity) | Low defectivity, missing linkers | HKUST-1 (SURMOF) | 2012 | |
Incorporation of defective linkers | Defective linkers create partial ‘missing linker’ defects. | HKUST-1(Ru) | 2014 | |
Incorporation of defective linkers | Defective linkers create partial ‘missing linker’ defects. | HKUST-1 | 2014 | |
Reversible linker dissociation | Reversible linker dissociation implicated in catalysis | HKUST-1 | 2014 | |
Linker fragmentation | Incorporating defects to modulate gas uptake properties | NU-125, HKUST-1 | 2014 | |
Doping structure with defective linkers | Mixture of missing cluster defects as well as partial missing linker defects and reduced Ru centres. | HKUST-1(Ru) | 2016 | |
Defective linker and variation of synthesis parameters | Defective CuII-CuI nodes, missing cluster defects | HKUST-1 | 2017 | |
Layer by layer thin film growth incorporating sonication | Minimal defectivity | HKUST-1 | 2017 | |
Water modulated, synthesis of MOF thin films | Reduced defectivity | HKUST-1 (SURMOF) | 2018 | |
Post-synthetic acid etching strategy | The disassembly of a cluster and linkers | HKUST-1 | 2019 | |
Defective linker introduced by ‘mixing’ or ‘alternating’ method during thing film synthesis to tune defect formation | Defective CuII-CuI nodes | HKUST-1 (SURMOF) | 2020 | |
Thermal treatment | Coordinatively unsaturated sites, reduced Ru/Rh centres | Ru/Rh HKUST-1 | 2020 | |
Liquid/Salt assisted grinding, treatment with alcohols | CuI defects, dissociated carboxylate sites | HKUST-1 | 2020 | |
Defective linker strategy | Defect type and distribution characterised using Raman micro-spectroscopy. | HKUST-1 | 2020 | |
Defective linker strategy | Defect type and distribution characterised by full-field tomographic X-ray adsorption spectroscopy. | HKUST-1 | 2021 | |
Thermally induced decarboxylation, reversible under CO2 treatment | Defective CuII-CuI nodes, predominantly at surface | HKUST-1 | 2021 | |
MIL series | ||||
Microwave-assisted solvothermal synthesis with urea modulator | Ligand replacement | MIL-53(Al) | 2018 | |
Structural evolution under electron beam | Structural rearrangement, deformation of crystal | MIL-101(Cr) | 2020 | |
Photothermal treatment of MIL-125(Ti)-NH2 in presence of Triethanolamine reduces TiIV to TiIII, weakening coordination bonds and thereby facilitating missing linker defect formation. | Missing linker defects | MIL-101(Ti)-NH2 | 2020 | |
Microwave synthesis at low temperature | Missing linkers | MIL-125 | 2022 | |
Reversible photo-induced metal-linker dissociation | Reversible linker dissociation | MIL-101(Fe) | 2023 | |
MgMOF-74 | ||||
Graphene oxide modulator | Missing cluster defects | Mg-MOF-74 | 2023 | |
Solvothermal synthesis, in-situ formation of formate | Missing linker (formate substitution) | Mg-MOF-74 | 2023 | |
Solvothermal synthesis, defective linker strategy | Unsaturated metal centres formed by insufficient donors on defective linker (1,4-benzenedicarboxylate) | Mg-MOF-74 | 2023 | |
MUV series | ||||
Synthesis in sub-stoichiometric linker conditions | Missing cluster vacancies | MUV-10 | 2021 | |
Solvothermal, systematic investigation into effect of modulator | Up to 40% missing linker defects | MUV-10 | 2021 | |
Solvothermal, systematic investigation using variety of chemically functionalised modulators | Missing linker/cluster defects | MUV-10 | 2022 | |
Solvothermal, hydroxy- or fluoro-isophthalic acid modulators | Defect extent tuned by modulator choice. Effect of defects on photocatalytic activity. | MUV-10 | 2022 | |
NOTT-100 | ||||
Thermal treatment or defective linker strategy | Coordinatively unsaturated sites, defective CuII-CuI nodes | NOTT-100 | 2020 | |
Incorporation of defective linkers | Coordinatively unsaturated sites, defective CuII-CuI nodes | NOTT-100 | 2020 | |
ZIF series | ||||
NA | Density Functional Theory based study of defect propagation in ZIFs. | ZIF-8 | 2019 | |
60Co gamma radiation employed to generate defects under ambient conditions | Extensive missing linker defects | ZIF-7 | 2023 | |
ZIF-8 thin films and powders | Missing linker and cluster defects identified via vibrational spectra, molecular dynamics simulations | ZIF-8 | 2024 | |
MOF-808 | ||||
Solvothermal, linker/SBU ratio 1:3, 2 days (compared to 1:1 and 7 days for pristine sample) | Missing linker defects | MOF-808 | 2021 | |
Solvent free synthesis. Precursors are ground in mortar and pestle, then crystallised in autoclave at temperatures between 90–130 °C. | Missing linker/cluster defects. | MOF-808 | 2023 | |
Defective linker strategy | Defective Zr-oxo cluster nodes due to incorporation of bi- rather than tri-carboxylate linkers. | MOF-808 | 2024 | |
Defective linker strategy | Defective Zr-oxo cluster nodes due to incorporation of bi- rather than tri-carboxylate linkers. | MOF-808 | 2024 | |
Miscellaneous frameworks | ||||
Thermal treatment induces defect formation in surface mounted MOF | CuI-CuII node defects with missing linkers | UHM-3 | 2015 | |
Competitive coordination strategy using Lauric acid. | Hierarchical porosity arising from missing linkers/clusters | MOF-5 | 2016 | |
Solvothermal synthesis, using L-lac or propanoic acid as modulator to generate missing linker defects. | Missing linker defects impact chiral separation capacity of homochiral framework. | [Zn2(bdc)(L-lac)(dmf)]b | 2017 | |
Multistep post-synthetic partial linker exchange | Ditopic linker partially exchanged for monotopic pyridine-carboxylate (missing linker defects) which form a trans-pyridine binding site for metalation. | PCN-160 | 2018 | |
Solvothermal synthesis, systematic variation of reaction conditions to promote phase purity and modulate defectivity | Sterically demanding modulators found to favour missing cluster defects. Smaller and moderately acidic modulators predominantly generated missing linker defects. | PCN-222, PCN-223, MOF-525 | 2019 | |
Solvothermal synthesis | Missing linker defects featuring bridging or mono-dentate methoxide (depending on the activation temperature). | COK-47 | 2019 | |
Solvothermal synthesis (intrinsic defectivity) | Missing linkers | PCN-221 | 2021 | |
Synthesis with linker mixture | Formation of CuI-CuII coordinatively unsaturated sites | Cu-BDC | 2022 | |
Reversible defect formation upon guest sorption | Reversible linker dissociation | Cu2(BDC)2DABCOb | 2022 | |
Incorporation of defective linkers | Coordinatively unsaturated sites, defective CuII-CuI nodes | [Cu2(Me-trz-ia)2]b | 2024 | |
