Functional porous metal–organic frameworks (MOFs) have been explored for a number of potential applications in catalysis, chemical sensing, water capture, gas storage, and separation. MOFs are among the most promising candidates to address challenges facing our society related to energy and environment, but the successful implementation of functional porous MOF materials are contingent on their stability; therefore, the rational design of stable MOFs plays an important role towards the development of functional porous MOFs. In this Focus article, we summarize progress in the rational design and synthesis of stable MOFs with controllable pores and functionalities. The implementation of reticular chemistry allows for the rational top-down design of stable porous MOFs with targeted topological networks and pore structures from the pre-selected building blocks. We highlight the reticular synthesis and applications of stable MOFs: (1) MOFs based on high valent metal ions ( e.g. , Al 3+ , Cr 3+ , Fe 3+ , Ti 4+ and Zr 4+ ) and carboxylate ligands; (2) MOFs based on low valent metal ions ( e.g. , Ni 2+ , Cu 2+ , and Zn 2+ ) and azolate linkers. We envision that the synthetic strategies, including modulated synthesis and post-synthetic modification, can potentially be extended to other more complex systems like metal-phosphonate framework materials.
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Aperiodic metal–organic frameworks
Metal–organic frameworks (MOFs) represent one of the most diverse structural classes among solid state materials, yet few of them exhibit aperiodicity, or the existence of long-range order in the absence of translational symmetry. From this apparent conflict, a paradox has emerged: even though aperiodicity frequently arises in materials that contain the same bonding motifs as MOFs, aperiodic structures and MOFs appear to be nearly disjoint classes. In this perspective, we highlight a subset of the known aperiodic coordination polymers, including both incommensurate and quasicrystalline structures. We further comment upon possible reasons for the absence of such structures and propose routes to potentially access aperiodic MOFs.
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- Award ID(s):
- 1645232
- PAR ID:
- 10279277
- Date Published:
- Journal Name:
- Chemical Science
- Volume:
- 11
- Issue:
- 41
- ISSN:
- 2041-6520
- Page Range / eLocation ID:
- 11094 to 11103
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Ammonia is a widely used toxic industrial chemical that can cause severe respiratory ailments. Therefore, understanding and developing materials for its efficient capture and controlled release is necessary. One such class of materials is 3D porous metal‐organic frameworks (MOFs) with exceptional surface areas and robust structures, ideal for gas storage/transport applications. Herein, interactions between ammonia and UiO‐67‐X (X: H, NH2, CH3) zirconium MOFs were studied under cryogenic, ultrahigh vacuum (UHV) conditions using temperature‐programmed desorption mass spectrometry (TPD‐MS) and in‐situ temperature‐programmed infrared (TP‐IR) spectroscopy. Ammonia was observed to interact with μ3−OH groups present on the secondary building unit of UiO‐67‐X MOFs via hydrogen bonding. TP‐IR studies revealed that under cryogenic UHV conditions, UiO‐67‐X MOFs are stable towards ammonia sorption. Interestingly, an increase in the intensity of the C−H stretching mode of the MOF linkers was detected upon ammonia exposure, attributed to NH−π interactions with linkers. These same binding interactions were observed in grand canonical Monte Carlo simulations. Based on TPD‐MS, binding strength of ammonia to three MOFs was determined to be approximately 60 kJ mol−1, suggesting physisorption of ammonia to UiO‐67‐X. In addition, missing linker defect sites, consisting of H2O coordinated to Zr4+sites, were detected through the formation of
n NH3⋅H2O clusters, characterized through in‐situ IR spectroscopy. Structures consistent with these assignments were identified through density functional theory calculations. Tracking these bands through adsorption on thermally activated MOFs gave insight into the dehydroxylation process of UiO‐67 MOFs. This highlights an advantage of using NH3for the structural analysis of MOFs and developing an understanding of interactions between ammonia and UiO‐67‐X zirconium MOFs, while also providing directions for the development of stable materials for efficient toxic gas sorption.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d0sc04798h
