Enabling Solution Processable COFs through Suppression of Precipitation during Solvothermal Synthesis
Safiya Khalil1, Matthew D Meyer2, Abdullah Alazmi1
1Department of Chemical and Biomolecular Engineering, Rice University, 6100 Main Street, MS-362, Houston, Texas 77005, United States.
ACS Nano
|November 22, 2022
Summary
Researchers developed a new method to create processable covalent organic frameworks (COFs). This technique yields stable nanoparticle suspensions, enabling the fabrication of COF materials like membranes and films for diverse applications.
Area of Science:
- Materials Science
- Nanotechnology
- Chemical Engineering
Background:
- Covalent organic frameworks (COFs) are promising nanoporous materials.
- Current synthesis methods produce insoluble COF aggregates, hindering practical applications.
- Solution-processing techniques are desirable for COF material fabrication.
Purpose of the Study:
- To develop a novel COF synthesis method yielding processable nanoparticle suspensions.
- To enable the fabrication of COF-based materials using conventional solution-processing techniques.
- To demonstrate the versatility of the method across different COF chemistries and structures.
Main Methods:
- Utilized a polar solvent, diacid catalyst, and slow reagent mixing at elevated temperatures.
- Achieved stable, homogeneous crystalline COF nanoparticle suspensions.
- Induced thermoreversible gelation upon cooling to form porous COF materials.
- Investigated compatibility with various COF types (imine, hydrazone) and topologies (rhombic, hexagonal).
Main Results:
- Successfully produced stable, homogeneous suspensions of crystalline COF nanoparticles.
- Demonstrated the ability to form COF monoliths, membranes, and films via solution processing.
- Confirmed excellent crystallinity and tunable porosity (micro- and macropores) in the synthesized COFs.
- Observed nanoparticle growth and gelation transition in suspensions.
- Prepared imine COF membranes exhibiting size-dependent polyethylene glycol (PEG) rejection.
Conclusions:
- A versatile solution-processing strategy for crystalline and porous COF materials has been established.
- The developed method overcomes previous limitations of COF insolubility and aggregation.
- This advancement is expected to significantly accelerate the development and application of COFs.
Related Concept Videos
01:09Colloidal precipitates
719
The high insolubility of some precipitates can result in an unfavorable relative supersaturation. This can lead to colloidal particles with a large surface-to-mass ratio, where adsorption is promoted. For instance, in the precipitation of silver chloride, silver ions are adsorbed on the surface of the colloidal particles, forming a primary layer. This layer attracts ions of opposite charge (such as nitrate ions), forming a diffuse secondary layer of adsorbed ions. This electric double layer...
719
01:12Precipitation Processes
557
The experimental conditions in a gravimetric analysis should be optimized to maximize the particle size and purity of the obtained precipitate. Ideally, the concentration of the precipitating reagent should be low with effective stirring to maintain low relative supersaturation for the growth of large crystals. In homogeneous precipitation, the precipitant is slowly generated by a chemical reaction in the solution to avoid local reagent excesses. For example, urea decomposes gradually to...
557
01:17Precipitation and Co-precipitation
1.9K
Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
1.9K
01:10Types of Coprecipitation
775
Coprecipitation is the contamination of a precipitate by otherwise soluble species and occurs via different processes. In colloidal precipitates, coprecipitation occurs via surface adsorption. For instance, barium sulfate has a primary layer of adsorbed barium ions and a secondary layer of nitrate counterions. This results in contamination of the precipitate by barium nitrate.
Sometimes, ions in a crystal lattice can undergo isomorphous replacement by inclusions of similar charge and size. For...
Sometimes, ions in a crystal lattice can undergo isomorphous replacement by inclusions of similar charge and size. For...
775
03:11Precipitation of Ions
28.1K
Predicting Precipitation
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
The equation that describes the equilibrium between solid calcium carbonate and its solvated ions is:
28.1K
00:49Gravimetry: Inorganic And Organic Precipitating Agents
1.4K
In gravimetry, the precipitant is chosen carefully to obtain a pure solid that can be easily filtered. Common inorganic precipitants can be used to determine several cations and anions. In some cases, the formation of the same precipitate can be used to determine the cation and the anion. For example, the reaction of barium and chromate ions to give barium chromate is used to determine both barium and chromate. However, precipitates such as hydroxides, oxalates, and metal ammonium phosphates...
1.4K