Revisiting the MIL-101 metal–organic framework: design, synthesis, modifications, advances, and recent applications

Abstract

Metal-organic frameworks (MOFs) have expanded into a burgeoning topic in materials science and engineering. Their success mostly stems from the versatility of their structure that can be diversely designed by...

Multivariate metal–organic framework MTV-MIL-101 via post-synthetic cation exchange: is it truly achievable?

“…For example, in Bureekaew's et al attempt to synthesize MIL-101(Cr/Fe) via the hydrothermal route, the SEM images of the sample with 15 mol% initial Fe concentration revealed the presence of some hexagonal MIL-88 crystals among the products. 6,48 Also, PSE provides more control on the exchanged percentage of the metal cations corresponding to the initially introduced one. For instance, in the attempt of synthesizing MIL-101(Cr/Fe) via the microwave-assisted technique, 47 the final product ended up containing <70 mol% Fe despite being introduced in a much lower percentage around 33 mol% since the applied conditions favored the formation of the product from Fe rather than Cr.…”

“…25 Lately, our group has reviewed the synthesis of the singlemetal MIL-101 structure from different metal sources and their recent application in different fields. 6 Attempts to achieve mixed-metal MIL-101 from multiple metal bases were also reported several times in the literature. Such mixed-metal frameworks, mostly bimetallic ones, were proven to have an improved/synergistic performance over monometallic structures.…”

“…[1][2][3][4][5] MIL-101 is considered one of the most enticing MOFs due to its robust structure, high specific surface area (SSA, S BET ≥ 4000 m 2 g −1 ) and pore volume (V pore ≥ 2.0 cm 3 g −1 ), remarkable chemical stability in air, water, acids, and bases, besides its moderate thermal stability (around 300 °C). [6][7][8] The properties of MOFs depend on the nature of their active components as well as their structure. Hence, the reconstruction of the MIL-101 framework with different compositions modifies its properties and may contribute to tailoring them towards desired structure and morphology for enhanced performance.…”

“…27,[32][33][34] Usually, MTV-MOFs are obtained either through direct synthesis or post-synthetic exchange (PSE). 6,27,35,36 Direct synthesis includes mixing the desired components prior to reaction and heating the mixture at a specific temperature and for a specific time, which are the same as those for the parent MOF synthesis. Alternatively, PSE encompasses the synthesis of the desired MOF first, followed by a set of processes to exchange one of the main components with another of a similar nature.…”

“…9,23,24 On the contrary, the direct synthesis of single-metal MIL-101s does not yield comparable textural properties: MIL-101s of different metal bases did not exhibit matching SSAs due to the sensitivity of each metal type to the applied reaction conditions. 6,8,9,13 Moreover, changes in the reaction conditions can give rise to other untargeted structures ( polymorphs or framework isomers) rather than MIL-101. 17 In conclusion, the formation of MIL-101 polymorphs of the same chemical components but of different networks, like MIL-88 and MIL-53, are highly influenced by the synthesis environment.…”