Published: May 12th, 2023
Here, we describe a protocol for the synthesis of low-valent metal-organic frameworks (LVMOFs) from low-valent metals and multitopic phosphine linkers under air-free conditions. The resulting materials have potential applications as heterogeneous catalyst mimics of low-valent metal-based homogeneous catalysts.
Metal-organic frameworks (MOFs) are the subject of intense research focus due to their potential applications in gas storage and separation, biomedicine, energy, and catalysis. Recently, low-valent MOFs (LVMOFs) have been explored for their potential use as heterogeneous catalysts, and multitopic phosphine linkers have been shown to be a useful building block for the formation of LVMOFs. However, the synthesis of LVMOFs using phosphine linkers requires conditions that are distinct from those in the majority of the MOF synthetic literature, including the exclusion of air and water and the use of unconventional modulators and solvents, making it somewhat more challenging to access these materials. This work serves as a general tutorial for the synthesis of LVMOFs with phosphine linkers, including information on the following: 1) the judicious choice of the metal precursor, modulator, and solvent; 2) the experimental procedures, air-free techniques, and required equipment; 3) the proper storage and handling of the resultant LVMOFs; and 4) useful characterization methods for these materials. The intention of this report is to lower the barrier to this new subfield of MOF research and facilitate advancements toward novel catalytic materials.
Metal-organic frameworks, or MOFs, are a class of crystalline, porous materials1. MOFs are constructed from metal ions or metal ion cluster nodes, often referred to as secondary building units (SBUs), and multitopic organic linkers to give two- and three-dimensional network structures2. Over the past three decades, MOFs have been studied extensively due to their potential use in gas storage3 and separation4, biomedicine5, and catalysis6. The overwhelming majority of MOFs reported are composed of high-oxidation state metal node....
1. Setting up the Schlenk line
The successful synthesis of Sn1-Pd produces a bright yellow, crystalline solid. The Pd(0) MOF products using analogous tetratopic phosphine linkers are also yellow. The most effective way to determine if the reaction was successful is to collect the PXRD pattern and evaluate the crystallinity of the sample. For example, Figure 2 shows the PXRD pattern of crystalline Sn1-Pd. The key features to verify that the sample is crystalline are that the reflection pea.......
There are several critical steps in the protocol that must be followed in order to achieve the desired phosphine-based LVMOF product with sufficient crystallinity. The first is that the metal precursor and modulator mixture (in this case, tetrakis(triphenylphosphine)palladium(0) and triphenylphosphine, respectively) must be dissolved independently of the multitopic phosphine linker (in this case, Sn1). This is to avoid the rapid and irreversible formation of amorphous coordination polymers, which occurs .......
|2800 Ultrasonic Cleaner, 3/4 Gallon, 40 kHz
|Used for sonicating
|Argon, Ultra High Purity
|Used as inert gas source
|D8 ADVANCE Powder X-Ray Diffractometer
|Used to collect PXRD patterns
|Chemglass Life Sciences
|Dewar used for liquid nitrogen
|Flask, High Vacuum Valve, Capacity (mL) 10, Valve Size 0-4 mm
|Reaction vessel referred to as "10 mL flask"
|Grade 2 Qualitative Filter Paper, Standard, 42.5 mm circle
|Used for product isolation
|Methylene Chloride (HPLC)
|Dried and deoxygenated prior to use
|Sn1 (tetratopic phosphine linker)
|Prepared according to literature procedure (ref. 15)
|SuperNuova+ Stirring Hotplate
|Thermo Fisher Scientific
|Used to heat oil bath
|Tetrakis(triphenylphosphine) palladium(0), 99% (99.9+%-Pd)
|Commercial Pd(0) source
|Dried and deoxygenated prior to use
|Triphenylphosphine, ≥95.0% (GC)
|Used as a modulator
|Used for solid addition
Copyright © 2024 MyJoVE Corporation. All rights reserved