Modulated formation of metal-organic frameworks by oriented growth over mesoporous silica

Abstract

Engineering the structure of metal-organic frameworks at the molecular level is of major interest for taking MOFs beyond their uses as bulk materials and creating multifunctional features with advanced applications. The notion involves directing MOF structure and controlling crystallization in terms of phase and orientation through interactions with directing agents. We have successfully used different concentrations of SBA-15 mesoporous silica for directed growth of the archetypal MOF-5 microcrystals along preferred crystallographic orientations, resulting in the production of interesting flower-like and nanorod frameworks instead of the conventional cubic structure. The results point to the possibility of using mesoporous silicas for designation of a wide range of MOF structural motifs with expedient performance and applications via selective interactions of MOF crystal building blocks with active functionalities on mesoporous surface, allowing heterogeneous seeding and controlled expansion of the framework along a preferred direction. The modifications in MOF structure have proven to improve the catalytic performance of MOF-silica nanocomposites up to 50% for Friedel-Crafts alkylation, compared to pure MOF-5. By discussing the effect of MOF texture on catalytic performance, this research aims to take MOF-5 beyond its bulk applications and opens up a new paradigm to design highly active and selective green heterogeneous catalysts based on MOFs.

Zr‐Metal Organic Framework and Derivatives for Adsorptive and Photocatalytic Removal of Acid Dyes

“…In addition, UiO-66 particles in UiO-66-CNT sample seemed to be slightly larger than pristine UiO-66 and UiO-66-NH2. It has been reported that the existence of external component could alter the growth direction and size (Karimi and Morsali, 2013). The larger UiO-66 particles might be due to the suspended CNTs in DMF, which affected the growth of UiO-66.…”

Mesoporous Metal–Organic Frameworks: Synthetic Strategies and Emerging Applications

“…Though a microporous MOF was chosen as demonstration, it shows greater promises for the future development of mesoporous MOFs with 2D morphologies, for their relatively larger pore sizes often make it harder to elaborately control the orientation of the framework crystallization. Similarly, modulated formation of oriented growth over mesoporous silica has also been conducted . Karimi et al used different concentrations of SBA‐15 mesoporous silica for the formation and growth of the MOF‐5 microcrystals along specific orientations, which leads to the samples of flower‐like or nanorod structures rather than a cubic one.…”

“…k) TEM images of MS/2, m) the SBA‐15 in MS/2 composite, and n) MS/3. Reproduced with permission . Copyright 2013, The Royal Society of Chemistry.…”

Advances of Metal‐Organic Frameworks in Energy and Environmental Applications

“…[49][50][51] The other method is direct insertion of presynthesized nanoparticles such as metal, metal oxide, POMs, organic polymers, carbon-based materials, SiO 2 into MOF pores or mixing nanoparticles into MOF precursors by solvothermal synthesis, making MOF materials around the nanoparticles. [52][53][54][55][56][57][58] In the latter method, the nanoparticles are usually decorated with suitable surface functional groups which can enhance the combination of nanoparticles and MOFs. [59] For MOFs acting as functional species, direct dispersion of MOF nanoparticles within the meso-/macroporous materials such as polymers, carbon-based materials and SiO 2 , and immersion of meso-/macroporous materials in MOF precursors under solvothermal synthesis are all effective strategies to construct MOF composites.…”