Engineering UiO‐66 Metal Organic Framework for Heterogeneous Catalysis

Abstract

frameworks (MOFs) are currently attracting considerable attention as heterogeneous catalysts at moderate temperatures, mainly for liquid-phase reactions. Since structural stability is one of the major concerns for the use of MOFs in catalysis, particularly considering that frequently some of the reported MOF materials are very unstable, the interest in this area has been focused on those MOFs exhibiting the highest structural robustness, UiO-66 being among the most widely used. Two introductory sections deal with the synthesis, structure and main properties of UiO-66, including its remarkable thermal (up to 350°C) and chemical (aqueous solution in a wide pH range) stability. The main body of the review summarizes those examples of using UiO-66 in catalysis grouped according to the nature of the active sites, starting with the use of UiO-66 as Lewis acids. In this section, emphasis has been made in the recent strategies to create structural defects in a controlled way that generate Lewis acidity. Other sections cover examples illustrating substituted terephthalate as active sites and the evidence that there is a synergy between acid and basic sites in close proximity that make some of these UiO-66 with substituents at the linker to act as dual acid-base catalysts. Other sections are focused on the use of UiO-66 as hosts of metal nanoparticles, metal oxides and other host, remarking the influence that the nature of UiO-66 and the possible presence of substituents in the framework play on the activity of the incorporated guest. The last section summarizes the current state of the art in the use of UiO-66 in catalysis and provides our views on future developments regarding the application of UiO-66 in industrial processes.

Influence of oxophilic behavior of UiO‐66(Ce) metal–organic framework with superior catalytic performance in Friedel‐Crafts alkylation reaction

“…UiO‐66(Zr) solid, [Zr 6 O 4 (OH) 4 (BDC) 6 ] (BDC: 1,4‐benzenedicarboxylic acid) was synthesized by the solvothermal method using Zr 4+ as metal ion and BDC as the organic ligand. During the crystal growth of UiO‐66(Zr), Zr 4+ cations self‐assemble to hexanuclear [Zr 6 O 4 (OH) 4 ] 12+ clusters which are coordinated by BDC ligands to 12 neighboring secondary building units in a face‐centered cubic arrangement . The structural analysis of UiO‐66(Zr) exhibits two types of cages with a large octahedral cage (0.9 nm) and a smaller tetrahedral cage (0.7 nm) that can be accessed through triangular windows of about 0.6 nm with the surface area ranging between 1000 and 1500 m 2 /g depending on preparation methods .…”

Copper(II) Oxide Nanoparticles Impregnated on Melamine‐Modified UiO‐66‐NH2 Metal–Organic Framework for C–N Cross‐Coupling Reaction and Synthesis of 2‐Substituted Benzimidazoles

“…In contrast, MOFs, as tailor‐made frameworks, are typically prepared via a simple and straightforward reaction in milder condition, and their functionality and porosity are easily tunable. Among MOFs, zirconium‐based MOF (UiO‐66‐NH 2 ) has high thermal stability (up to 375°C) and remarkable tolerance in a broad range of pH . Consequently, MOFs provide many advantages (e.g.…”

“…Consequently, MOFs provide many advantages (e.g. large pore size for easy and fast mass transfer, shape selective for reactants, and confinement effect for encapsulation of the catalyst species) as supports for catalysis in comparison with inorganic porous materials.…”

UiO‐66 microcrystals catalyzed direct arylation of enol acetates and heteroarenes with aryl diazonium salts in water

“…in [Zr 6 (μ 3 ‐O) 4 (μ 3 ‐OH) 4 (BDC) 6 ] (H 2 BDC = terephthalic acid). The metal‐cluster based Lewis acidity endows UiO‐66 favorable in the synthesis of a large variety of aromatic compounds including heterocycles by the introduction of defects . On the other hand, the composition of UiO‐66 or amino‐functionalized NH 2 ‐UiO‐66 with noble metals, such as Ag, Pd and Pt, lead to good catalysis performance in carboxylation, reduction of nitroarenes, esterification, dehydrogenation of formic acid, and Suzuki coupling .…”