Work

Toward Reversible Crystalline-to-Amorphous Guest-Induced Transitions in Manganese(III) Carboxylate Metal–Organic Frameworks

Year: 2025

Type: article

Abstract: Metal–organic frameworks (MOFs) are an interesting class of inorganic/organic hybrid materials with a wide scope of applications. Although manganese is an abundant metal, the synthesis of Mn(III)-containing MOFs has not been widely studied due to the relative redox sensitivity of this species. We therefore investigated the self-oxidation of manganese(II) nitrate in the presence of aromatic dicarboxylic linkers in alcohols, discovering a series of new Mn(III)-MOFs. The obtained structures were analyzed through a combination of (synchrotron) X-ray diffraction and total scattering (pair distribution function analysis) experiments. In methanol, the syntheses led to new nonflexible members of the MIL-47/MIL-53 and MIL-69 families of MOFs, rare examples containing bridging methoxy anions. When using ethanol or 1-propanol, wine rack-like structures (named UcL-1 and UcL-2) with different Mn II /Mn III secondary building units are obtained. These demonstrate intriguing reversible crystalline-to-crystalline and crystalline-to-amorphous transitions upon guest exchange and release. The latter process involves strong correlated and noncorrelated structural distortions, paired with the creation of coordinatively unsaturated Mn III sites. This work demonstrates that Mn(III)-containing carboxylate systems have the potential for the design of new functional MOF materials, including structures with tunable flexible behavior.

Source: Inorganic Chemistry

DOI: 10.1021/acs.inorgchem.4c05337