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Fabrizio K, Gormley EL, Davenport AM, Hendon CH, Brozek CK. Gram-scale synthesis of MIL-125 nanoparticles and their solution processability. Chem Sci 2023; 14:8946-8955. [PMID: 37621428 PMCID: PMC10445466 DOI: 10.1039/d3sc02257a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 07/30/2023] [Indexed: 08/26/2023] Open
Abstract
Although metal-organic framework (MOF) photocatalysts have become ubiquitous, basic aspects of their photoredox mechanisms remain elusive. Nanosizing MOFs enables solution-state techniques to probe size-dependent properties and molecular reactivity, but few MOFs have been prepared as nanoparticles (nanoMOFs) with sufficiently small sizes. Here, we report a rapid reflux-based synthesis of the photoredox-active MOF Ti8O8(OH)4(terephthalate)6 (MIL-125) to achieve diameters below 30 nm in less than 2 hours. Whereas MOFs generally require ex situ analysis by solid-state techniques, sub-30 nm diameters ensure colloidal stability for weeks and minimal light scattering, permitting in situ analysis by solution-state methods. Optical absorption and photoluminescence spectra of free-standing colloids provide direct evidence that the photoredox chemistry of MIL-125 involves Ti3+ trapping and charge accumulation onto the Ti-oxo clusters. Solution-state potentiometry collected during the photochemical process also allows simultaneous measurement of MOF Fermi-level energies in situ. Finally, by leveraging the solution-processability of these nanoparticles, we demonstrate facile preparation of mixed-matrix membranes with high MOF loadings that retain the reversible photochromism. Taken together, these results demonstrate the feasibility of a rapid nanoMOF synthesis and fabrication of a photoactive membrane, and the fundamental insights they offer into heterogeneous photoredox chemistry.
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Affiliation(s)
- Kevin Fabrizio
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon Eugene OR 97403 USA
| | - Eoghan L Gormley
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon Eugene OR 97403 USA
| | - Audrey M Davenport
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon Eugene OR 97403 USA
| | - Christopher H Hendon
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon Eugene OR 97403 USA
| | - Carl K Brozek
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon Eugene OR 97403 USA
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Huang J, Marshall CR, Ojha K, Shen M, Golledge S, Kadota K, McKenzie J, Fabrizio K, Mitchell JB, Khaliq F, Davenport AM, LeRoy MA, Mapile AN, Debela TT, Twight LP, Hendon CH, Brozek CK. Giant Redox Entropy in the Intercalation vs Surface Chemistry of Nanocrystal Frameworks with Confined Pores. J Am Chem Soc 2023; 145:6257-6269. [PMID: 36893341 DOI: 10.1021/jacs.2c12846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Redox intercalation involves coupled ion-electron motion within host materials, finding extensive application in energy storage, electrocatalysis, sensing, and optoelectronics. Monodisperse MOF nanocrystals, compared to their bulk phases, exhibit accelerated mass transport kinetics that promote redox intercalation inside nanoconfined pores. However, nanosizing MOFs significantly increases their external surface-to-volume ratios, making the intercalation redox chemistry into MOF nanocrystals difficult to understand due to the challenge of differentiating redox sites at the exterior of MOF particles from the internal nanoconfined pores. Here, we report that Fe(1,2,3-triazolate)2 possesses an intercalation-based redox process shifted ca. 1.2 V from redox at the particle surface. Such distinct chemical environments do not appear in idealized MOF crystal structures but become magnified in MOF nanoparticles. Quartz crystal microbalance and time-of-flight secondary ion mass spectrometry combined with electrochemical studies identify the existence of a distinct and highly reversible Fe2+/Fe3+ redox event occurring within the MOF interior. Systematic manipulation of experimental parameters (e.g., film thickness, electrolyte species, solvent, and reaction temperature) reveals that this feature arises from the nanoconfined (4.54 Å) pores gating the entry of charge-compensating anions. Due to the requirement for full desolvation and reorganization of electrolyte outside the MOF particle, the anion-coupled oxidation of internal Fe2+ sites involves a giant redox entropy change (i.e., 164 J K-1 mol-1). Taken together, this study establishes a microscopic picture of ion-intercalation redox chemistry in nanoconfined environments and demonstrates the synthetic possibility of tuning electrode potentials by over a volt, with profound implications for energy capture and storage technologies.
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Affiliation(s)
- Jiawei Huang
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Checkers R Marshall
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Kasinath Ojha
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Meikun Shen
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Stephen Golledge
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Kentaro Kadota
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Jacob McKenzie
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Kevin Fabrizio
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - James B Mitchell
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Faiqa Khaliq
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Audrey M Davenport
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Michael A LeRoy
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Ashley N Mapile
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Tekalign T Debela
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Liam P Twight
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Christopher H Hendon
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Carl K Brozek
- Department of Chemistry and Biochemistry, Material Science Institute, University of Oregon, Eugene, Oregon 97403, United States
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