Nanoporous Covalent Organic Framework Embedded with Fe/Fe₃O₄ Nanoparticles as Air-Stable Low-Density Nanomagnets

Abstract

Covalent organic frameworks (COFs) made of light atoms such as H, C, N, and O with a significant void-to-framework ratio are excellent low-density supports for nanoparticles (nPs). Their framework can be precoded with heteroatoms to ensure binding with metallic nanoclusters. With these advantages, if controlled amounts of magnetic nPs are anchored to them, they can yield low-density organic−inorganic nanomagnets. Their organic nature facilitates fusion with bulk materials such as paper/textile to enable bulk composites with well-dispersed lowdensity magnets, which have potential for defense and nextgeneration aviation applications. Herein, we have grown small Fe/ Fe 3 O 4 nPs (5−18 wt %) inside a COF. Interestingly, 300 mg of this organic−inorganic framework material (containing 50 mg of nPs) can lift a vial of ∼15,000 mg (300 times heavier). Also, the hydrophobic COF wraps around the Fe/Fe 3 O 4 nanocluster retaining its room-temperature magnetic character even after 1 year, while the naked nPs lose it within a few days because of air oxidation. Bulk composites with paper and polymers have been made using this low-density Fe−COF to demonstrate their processability.

Functionalized magnetic covalent organic framework nanocomposites for high‐efficiency adsorption of ethyl carbamate from liquor

“…To further demonstrate the successful coating of COFs on the surface of Fe 3 O 4 , XPS was carried out for elemental analysis (Kushwaha et al., 2020). As we can see from the full spectrum (Figure S1A), the composite nanomaterials contain C, N, O, and Fe elements.…”

Metalated covalent organic frameworks: from synthetic strategies to diverse applications

“…Additionally, partial reduction of inorganic salts can give low-valent metal oxides. For example, FeCl 3 in the IISERP-COF6 COF was reduced with NaBH 4 to obtain Fe 3 O 4 @COF, 325 while the treatment of COFs with KMnO 4 led to COF-supported MnO 2 nanoparticles. 326,327 Table 3 provides more such examples.…”

Recent Advancements in the Fabrication of Functional Nanoporous Materials and Their Biomedical Applications

“…Crystalline nanoporous materials have a narrow pore size distribution and are suitable for molecular sieving filtration where uniformity in pore size is important [ 18 , 19 ]. Zeolites, metal organic frameworks (MOFs), and covalent organic frameworks are examples of crystalline nanoporous materials [ 20 , 21 , 22 ]. Nanoporous materials can also be subdivided based on the material type, i.e., inorganic (zeolites, mesoporous silica), metal-organic frameworks (MOFs), and covalent-organic frameworks (COFs).…”