How Does the Fluorination of the Linker Affect the Structural Chemistry of Trimesate‐Based Metal‐Organic Frameworks (MOFs)?

FMOFs, i.e. metal‐organic frameworks with linkers with fluoro substituents, were supposed to show enhanced thermal and chemical stability as well as high gas affinity and hydrophobicity. However, at least for aromatic carboxylate ligands it was shown in a subsequent work that fluoro substituents wea...

Ausführliche Beschreibung

Gespeichert in:
Bibliographische Detailangaben
Veröffentlicht in:Zeitschrift für anorganische und allgemeine Chemie (1950) 2020-07, Vol.646 (14), p.1157-1167
Hauptverfasser: Smets, Daniel, Ruschewitz, Uwe
Format: Artikel
Sprache:eng
Schlagworte:
Online-Zugang:Volltext
Tags: Tag hinzufügen
Keine Tags, Fügen Sie den ersten Tag hinzu!
Beschreibung
Zusammenfassung:FMOFs, i.e. metal‐organic frameworks with linkers with fluoro substituents, were supposed to show enhanced thermal and chemical stability as well as high gas affinity and hydrophobicity. However, at least for aromatic carboxylate ligands it was shown in a subsequent work that fluoro substituents weaken the C(phenyl)‐COO– bond and thus facilitate decarboxylation leading to a decreased chemical and thermal stability. Nonetheless, it was concluded that linker fluorination leads to a rich structural chemistry, as the torsion angle between the phenyl ring and the carboxylate group is significantly increased in these compounds. Here, we present the very first examples of four MOFs all based on Sr2+ cations and trimesate‐based linkers with three different degrees of fluorination as well as the known non‐fluorinated counterpart: [Sr(HL)(H2O)]·n H2O [1: L = mF‐BTC3–, n = 0.5, P1, Z = 2; 2: L = dF‐BTC3–, n = 0.5, C2/c, Z = 8; 3: L = pF‐BTC3–, n = 1.5, C2/c, Z = 8; 4: L = BTC3–, n = 0.5, P1, Z = 2; BTC3– ≡ 1,3,5‐benzenetricarboxylate (trimesate); mF‐BTC3– ≡ monofluorinated trimesate, dF‐BTC3– ≡ difluorinated trimesate, pF‐BTC3– ≡ per‐(tri‐)fluorinated trimesate]. Whereas 1 and known 4 are found to crystallize in isotypic structures and 2 in a very similar structural arrangement [all CN(Sr2+) = 9], 3 with the highest degree of fluorination exhibits a completely different crystal structure [CN(Sr2+) = 8], which is already obvious from the different composition. It is shown that the torsion angles between the phenyl ring and the carboxylate groups play an important structure‐directing role. DSC/TGA investigations confirm that with increasing fluorination the thermal stability is decreased. However, the release temperature of water, i.e. the affinity to water, increases with the number of fluoro substituents.
ISSN:0044-2313
1521-3749
DOI:10.1002/zaac.202000137