We report a synthetic methodology for decorating a surface of metal–organic frameworks (MOFs) with polymers through postsynthetic modification. Well-defined polymers with reversibly deactivated radical species at their chain end were reacted with vinyl-functionalized MOFs in the presence of a radical initiator. The radical addition forms a C–C bond between the polymer end with the functional group at the MOF ligand. We used sterically bulky star polymers containing electron-deficient maleimide chain ends, which facilitated modification of the external surface, yielding polymer-grafted MOF composite particles. A patchy MOF particle can also be obtained by simultaneously grafting two polymers and jammed at the immiscible liquid–liquid interface. We further show that the selective removal of a sacrificial polymer would partially expose the surface of MOFs to external environment, which hinders the uptake of macromolecular guests above the critical hydrodynamic size. Overall, four polymer@MOF composites have successfully been achieved through the present postsynthetic patchworks on MOFs with star polymers and selective etching process.

Fine-tuning and pore environment control of covalently connected metal–organic framework (MOF) and mixed-matrix membrane (MMM) composite materials were achieved. Core–shell-type, dual-functionalized, zirconium-based MOFs were prepared through a postsynthetic ligand exchange (PSE) process, and active vinyl functionalities on the surface of MOF nanoparticles were utilized for polymerization by forming interfacial-covalent connections between MOF nanoparticles and polymeric membranes via thiol–ene click photopolymerization. The target functionality of the MOF pore originated from the parent MOFs, allowing pore engineering of the MOF–MMM composite materials. A series of defect-free, interface-controlled, and core-functionalized MOF–MMMs were prepared through the present methodology, and the NO2-functionalized/covalently connected MOF–MMM showed the highest CO2 permeability and solubility without loss of selectivity. This facile and versatile approach will be useful for the fabrication of functional MOF nanoparticle-based membranes for various applications, such as catalysis and separation.

We developed a facile methodology for fabricating a free-standing mixed-matrix membrane (MMM) containing covalently incorporated metal–organic framework (MOF) particles up to 60 wt% by utilizing thiol–ene photopolymerization with the MOF consisting of vinyl functionality. Vinyl-functionalized UiO-66 (UiO-66-CH[double bond, length as m-dash]CH2) was synthesized from 2-vinyl-1,4-dicarboxylic acid with ZrCl4, and a free-standing MMM was readily produced by irradiation of a polymerization mixture containing UiO-66-CH[double bond, length as m-dash]CH2, poly(ethylene glycol) divinyl ether (PEO-250), pentaerythritol tetra(3-mercaptopropionate) (PETM), 2,2′-(ethylenedioxy)diethanethiol (EDDT), and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as a photoradical initiator. Assorted analyses combining FTIR, thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction strongly supported the fact that the desired MMM containing well-dispersed UiO-66-CH[double bond, length as m-dash]CH2 particles was successfully produced by C–S bond formation, which provided strong union of the MOF with the polymer matrix without interfacial voids. The produced MMM was highly flexible and showed improved mechanical properties as compared to the pristine polymeric membrane, indicating that the covalently immobilized UiO-66-CH[double bond, length as m-dash]CH2 particles were homogeneously distributed in the polymer matrix. Gas permeability across the MMM was significantly enhanced compared with the pristine polymeric membrane as diffusion of the gas molecules was facilitated in the porous space in the MOF.