Photoinduced Postsynthetic Polymerization of a Metal–Organic Framework toward a Flexible Stand‐Alone Membrane

Abstract

Metal-organic frameworks (MOFs) are a promising class of nanoporous polymeric materials. However, the processing of such fragile crystalline powders into desired shapes for further applications is often difficult. A photoinduced postsynthetic polymerization (PSP) strategy was now employed to covalently link MOF crystals by flexible polymer chains, thus endowing the MOF powders with processability and flexibility. Nanosized UiO-66-NH 2 was first functionalized with polymerizable functional groups, and its subsequent copolymerization with monomers was easily induced by UV light under solvent-free and mild conditions. Because of the improved interaction between MOF particles and polymer chains, the resulting stand-alone and elastic MOF-based PSPderived membranes possess crack-free and uniform structures and outstanding separation capabilities for Cr VI ions from water.Metal-organic frameworks (MOFs) are nanoporous polymeric materials constructed from metal ions or clusters that are covalently linked by organic ligands and thus possess the characteristics of both organic and inorganic materials.

Postsynthetic Modification: An Enabling Technology for the Advancement of Metal–Organic Frameworks

“…In 2015, Wang and co-workers developed the concept of postsynthetic polymerization (PSP). 44 In this report, PSM was first conducted on UiO-66-NH 2 by introducing methacrylic anhydride to install methacrylamide handles on amine groups of the MOF (UiO-66-NH 2 -Met). Subsequently, the methacrylamide handles on the MOF served as a polymerization point for butyl methacrylate (BMA), which was introduced in the presence of a photoinitiator (phenyl(2,4,6-trimethylbenzoyl)phosphine oxide) and UV light, resulting in a cross-linked MOF–polymer hybrid material.…”

Water-dispersible PEG-curcumin/amine-functionalized covalent organic framework nanocomposites as smart carriers for in vivo drug delivery

“…Using polymers to modify COFs could be a promising method to adjust the stability, dispersity, and flexibility of these porous crystalline solids. The integration of polymers and porous materials has been reported in metal-organic frameworks (MOFs)/polymer composites 29 – 31 , which could be pre-prepared 29 , 30 or post-prepared 31 by the formation of MOF crystals using polymeric linkers or the attachment of polymer chains onto the functional ligand of MOF crystals. An amine-functionalized COF-1 has been reported by mixing 3-aminopropyl triethoxysilane (APTES) into established COF-1 recipe via Brønsted-type interactions 25 .…”

Approaches and challenges in the synthesis of three-dimensional covalent-organic frameworks

“…Modification of internal structure of 3D frameworks requires ready access of reactant species to internal functionalization sites, which may impose additional barriers for the translation of 2D COF PSM techniques to their 3D counterparts. In contrast, PSM techniques developed for 3D MOFs, such as the introduction of polymerizable methacrylamide functionalities into MOF UiO-66 16 or the removal of photolabile o-nitrobenzyl pendant groups 81 , could be more readily implemented in 3D COFs.…”

“…ligands through coordination bonds, thus possessing both the chemical and structural tunability of the organic ligands, the coordination possibilities of various metal ions, and the uniform porosity and high surface area of a crystalline nanoporous material 3,[15][16][17] . Examples of this class of materials necessarily contain a large amount of potentially toxic or reactive metal centers, and their relatively weak coordination bonds exhibit varying stability under high humidity and temperature, conditions ubiquitous in industrial applications [18][19][20][21] .…”