Discovery of spontaneous de-interpenetration through charged point-point repulsions

• Published in: Chem Vol. 8; no. 1; pp. 225 - 242
• Main Authors: Hanna, Sylvia L., Chheda, Saumil, Anderson, Ryther, Ray, Debmalya, Malliakas, Christos D., Knapp, Julia G., Otake, Ken-ichi, Li, Peng, Li, Penghao, Wang, Xingjie, Wasson, Megan C., Zosel, Katarina, Evans, Austin M., Robison, Lee, Islamoglu, Timur, Zhang, Xuan, Dichtel, William R., Stoddart, J. Fraser, Gomez-Gualdron, Diego A., Gagliardi, Laura, Farha, Omar K.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 13.01.2022
• Subjects: charged point-point repulsion; entanglement; interpenetration; metal–organic framework; spontaneous; uranium; metal–organic framework; charged point-point repulsion; entanglement; interpenetration; uranium; spontaneous; SDG7: Affordable and clean energy
• ISSN: 2451-9294; 2451-9294
• DOI: 10.1016/j.chempr.2021.10.027

Energetically driven reduction of porosity through entanglement is ubiquitous in nature and synthetic systems. This entanglement decreases valuable internal pore space useful for applications, such as catalysis, storage, and sensing. Here, we describe the discovery of spontaneous de-interpenetration in a 6-fold interpenetrated uranium-based metal-organic framework (MOF), NU-1303-6. De-interpenetration transforms NU-1303-6 (14.2 and 19.8 Å pores) to its larger pore (40.7 Å) non-interpenetrated counterpart, which possesses a record-high 96.6% void fraction and 9.2 cm3g−1 pore volume. Density functional theory calculations reveal that charged point-point repulsions between anionic, closely positioned uranium-based nodes drive this phenomenon. These repulsions compete with water molecules that hydrogen bond nearby networks together, favoring interpenetration. Controlling the interplay between these intermolecular forces enables the reversal of omnipresent energetic equilibria, leading to thermodynamically favored open pore structures. The discovery of charged point-point repulsion will likely lead to the re-evaluation of non-interpenetrated network design, synthesis, and wide-reaching applications. [Display omitted] •Spontaneous de-interpenetration discovered in a uranium metal-organic framework•Charged point-point repulsions between anionic moieties drive de-interpenetration•De-interpenetration results in record-high void fraction and pore volume•This discovery enables thermodynamic syntheses of highly porous materials Entanglement is an energetically favorable occurrence, pervasive in both nature and synthetic systems, where networks prefer to entwine with one another rather than remain open and accessible. As a result of entanglement, valuable internal pore space, useful for applications such as catalysis, storage, and sensing, is lost. Here, we detail our discovery of a phenomenon termed “charged point-point repulsion,” which energetically favors dis-entanglement, transforming a densely packed uranium-based framework with 14.2 and 19.8 Å pores into an open material with 40.7 Å pores and record-high void fraction and pore volume. We anticipate that the phenomenon described in this work could be widely generalized for the direct and systematic production of non-entangled structures with an abundance of valuable pore space and far-reaching practical importance. More fundamentally, this study compels a re-evaluation of the thermodynamics of porosity. Entanglement, a thermodynamically favorable occurrence, is pervasive in both nature and synthetic systems; yet, it reduces valuable internal pore space in network materials. Here, we detail our discovery of spontaneous de-interpenetration driven by charged point-point repulsions. This phenomenon doubles the pore size of an initially 6-fold interpenetrated uranium-based metal-organic framework, NU-1303-6, resulting in record-high void fraction and pore volume. We expect that employing these design principles in other network materials will enable the facile synthesis of highly porous materials.