Modification and functionalization of MOFs and COFs have been targeted by researchers in different majors. Modification in MOFs and COFs could tune enhance many of the physical and chemical properties of the parent MOFs and COFs which in turn greatly affected the overall properties such as chemical and thermal stabilities, optical electrical performances, catalytic performance, gaseous or adsorbates uptake-release and host-guest interactions. The change of properties confers them more opportunities for potential applications. Alfa Chemistry's chemists have extensive experience in the modification of MOFs and COFs and we can modify any MOFs and COFs quickly and efficiently based upon your project needs.
Modification of MOFs and COFs can be carried out through pre-synthetic approach (bottom-up) and post-synthetic modification (PSM) approach. Although pre-synthetic approach has been used to construct modified MOFs and COFs, it suffers strong limitations such as the possibility that the as expected active group may react with other active sites and may be lost during synthesis. An alternative approach that can circumvent these limitations is PSM which is to chemically modify MOFs and COFs after the crystalline materials have already been formed. The method can introduce new functional groups on a pre-established MOFs and COFs skeleton while retaining the underlying topology, which provides a powerful method to construct functional MOFs and COFs. Based on this, Alfa Chemistry will mainly adopt PSM strategy to modify MOFs and COFs.
Fig. 1. Structural modification strategies of bottom-up and PSM (Take the COFs as example) .
Different types of PSM methods are adopted by Alfa Chemistry to prepare modified MOFs and COFs. For MOFs modification, PSM can be carried out by a number of approaches such as modifying the linker (ligand) and/or metal node, and adsorption/exchange of guest species. For COFs modification, PSM can be carried out by covalent and metalation modification of COFs. Details are shown in the following table.
|Available PSM methods
|Description and details
|PSM of MOFs
|Metal-Based PSM of MOFs
|The strategy is to modify MOFs through metal metathesis. The methods of metal metathesis include metal exchange, metal incorporation (metal doping) and metal exchange followed by oxidation.
|Ligand-Based PSM of MOFs
|The strategy is to modify the ligands or exchange the linkers, either partially or completely to achieve a new MOFs with better properties. The specific methods include ligand modification, ligand exchange, ligand installation and ligand removal.
|Guest-Based PSM of MOFs
|Customarily the pores of MOFs are occupied by various guest molecules. The strategy is replacement, removal or incorporation of the guest molecules to introduce new and exciting properties to the MOFs structure.
|PSM of COFs
|Covalent PSM of COFs
|The strategy involves functional group inter-conversion through different covalent reactions to introduce new and exciting properties. Covalent PSM of COFs includes covalent PSM of linkers and covalent PSM of linkages (The linkages include triazole linkage, ester linkage, amide linkage, sulfide linkage, o-carbamate linkage, ether linkage and oxime linkage).
|PSM of COFs through metalation
|The strategy to introduce inorganic metal ions such as Ca, Sr, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Mo, Rh, Pd, Re and Ir into COFs through treatment of COFs with salts of suitable inorganic ions taking advantage of metal–ligand interactions.
Fig. 2. Possible pathways of PSM in MOFs: a) metal exchange, b) metal incorporation, c) ligand exchange, d) ligand installation, e) ligand removal, and e) guest incorporation inside the pores .