Phase engineering of metal‐organic frameworks

Abstract

As an important category of porous crystalline materials, metal‐organic frameworks (MOFs) have attracted extensive research interests owing to their unique structural features such as tunable pore structure and enormous surface area. Besides controlling the size, dimensionality, and composition of MOFs, further exploring the crystal‐phase‐dependent physicochemical properties is essential to improve their performances in various applications. Recently, great progress has been achieved in the phase engineering of nanomaterials (PEN), which provides an effective strategy to tune the functional properties of nanomaterials by modulating the arrangement of atoms. In this review, we adopt “phase” instead of “topology” to describe the crystal structure of MOFs and summarize the recent advances in phase engineering of MOFs. The two main strategies used to control the phase of MOFs, that is, phase‐controlled synthesis and phase transformation of MOFs, will be highlighted. The roles of various reaction parameters in controlling the crystal phase of MOFs are discussed. Then, the phase dependence of MOFs in various applications including luminescence, adsorption, and catalysis are introduced. Finally, some personal perspectives about the challenges and opportunities in this emerging field are presented.

Copper-Based Metal–Organic Framework with a Tetraphenylethylene-Tetrazole Linker for Visible-Light-Driven CO2 Photoconversion

“…Metal–organic frameworks (MOFs), constructed from metal ions/clusters and organic linkers, have received extensive attention in material science and crystal engineering. − Due to their unique properties, including defined structures, an ordered porous environment, accessible active sites, and tunable chemical compositions, MOFs have shown unlimited potential in the field of photocatalytic CO 2 reduction. − N-rich ligands have been used as functional organic linkers for their appealing properties in increasing electrical conductivity, surface wettability, and high CO 2 affinity. − In recent years, N-rich MOFs, made from divalent metals such as Zn 2+ , Ni 2+ , or Co 2+ , have been developed rapidly for CO 2 photoreduction. − Compared to them, copper-based photocatalysts are also attractive in the field of CO 2 reduction due to their appropriate adsorption strength of reaction intermediates, the impressive capability of catalyzing CO 2 into multi-electron products, and low cost . Despite these merits, copper-based MOFs with efficient performance in CO 2 photocatalytic reduction remains a substantial challenge.…”

Luminescent Porphyrinic Metal–Organic Frameworks for Oxygen Sensing: Correlation of Nanostructure and Sensitivity

“…A comparison of typical reaction conditions for the PCN MOFs studied in this work (Supporting Information, Table S6) reveals significant differences in concentrations of the reagents, solvents, temperatures, duration of the reaction, Zr sources, and type of modulators. The choice of modulator is crucial for controlled crystallization of phase pure MOFs. ,, For PCN-222, stronger acidic modulators (dichloroacetic − acid or formic acid − ) are often used, compared to the weaker acids (propionic acid , or acetic acid − ) utilized in the synthesis of PCN-224, PCN-223, and MOF-525. On the other hand, one common modulator, benzoic acid, acts as a “universal modulator” and has been used for all porphyrinic MOFs (Supporting Information, Table S6). ,− In general, temperatures between 65 and 130 °C are preferred, while reaction times are varied in the hours to days range.…”

“…The choice of modulator is crucial for controlled crystallization of phase pure MOFs. 47,48,56 For PCN-222, stronger acidic modulators (dichloroacetic 57−59 acid or formic acid 60−62 ) are often used, compared to the weaker acids (propionic acid 63,64 or acetic acid 65−68 ) utilized in the synthesis of PCN-224, PCN-223, and MOF-525. On the other hand, one common modulator, benzoic acid, acts as a "universal modulator" and has been used for all porphyrinic MOFs (Supporting Information, Table S6).…”

Competing phases in the room-temperature M2(2,6-ndc)2(dabco) metal–organic framework thin film synthesis

“…However, there may be other synthesis parameters to optimise, since some MOF phases can form in a very narrow concentration, temperature, and pH range. [65][66][67] In order go through many synthesis conditions for M 2 (2,6-ndc) 2 (dabco) thin films, a faster synthesis strategy could be adopted, such as the use of an aluminium-doped ZnO functionalisation on the substrate surface. MOF growth then requires only one submersion in the metal salt solution followed by the ligand solution.…”