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Functionalization of metal−organic frameworks (MOFs) is critical in exploring their structural and chemical diversity for numerous potential applications. Herein, we report multiple approaches for the tandem postsynthetic modification (PSM) of various MOFs derived from Zr(IV), Al(III), and Zn(II). Our current work is based on our efforts to develop a wide range of MOF platforms with a dynamic functional nature that can be chemically switched via thermally triggered reversible Diels−Alder (DA) and hetero-Diels−Alder (HDA) ligations. Furan-tagged MOFs (furan-UiO-66-Zr) were conjugated with maleimide groups bearing dienophiles to prepare MOFs with a chemically switchable nature. As HDA pairs, phosphoryl dithioester-based moieties and cyclopentadiene (Cp)-grafted MOF (Cp-MIL-53-Al) were utilized to demonstrate the cleavage and rebonding of the linkages as a function of temperature. In addition to these strategies, the Michael addition reaction was also applied for the tandem PSM of IRMOF-3-Zn. Maleimide groups were postsynthetically introduced in the MOF lattice, which were further ligated with cysteine-based biomolecules via the thiol− maleimide Michael addition reaction. On the basis of the versatility of the herein presented chemistry, we expect that these approaches will help in designing a variety of sophisticated functional MOF materials addressing diverse applications.

Metal nanoparticles (NPs) confined on the surface of flexible polymers films are highly sought after for a diverse range of applications. Herein, we report a facile substrate-independent strategy for surface-confined growth of silver NPs (AgNPs) on the surfaces of chemically diverse flexible polymer film substrates represented by polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET). The surfaces of polymer films were subjected to ultraviolet-printing and conjugated to the hyperbranched polyethyleneimine (PEI). The PEI-functionalized surfaces were subjected to surface-confined growth of AgNPs via three approaches. Besides PEI, the ability of quaternary amine and carboxylic acid functional groups to assist surface-confined growth of AgNPs is also evaluated. All the films with surface-confined AgNPs exhibited absorbance due to the surface plasmon resonance (SPR) characteristic of AgNPs. The AgNPs confined on the surface of PP films were functionalized with 4-mercaptobenzoic acid, and the λ max for SPR absorbance of the resulting platform was found to exhibit a markedly higher bathochromic shift when exposed to Cu 2+ ions. This Cu 2+ ions sensor could sense Cu 2+ ions with a limit of detection of 2.6 ppm. Besides Cu 2+ sensing via a bathochromic shift in λ max for SPR absorbance, the SPR absorbance of AgNPs confined on the surface of PP films was found to diminish upon exposure to the aqueous solution of sodium hydrosulfide (NaSH), which acts as a hydrogen sulfide (H 2 S) donor. The intensity of the SPR absorbance was found to decrease >40% upon exposure to 5 μM aqueous NaSH solution, whereas the SPR signal almost completely disappeared with visual decoloration when the films were exposed to 50 μM aqueous NaSH solution. This highlights the H 2 S sensing ability of the AgNPs confined on the surface of PP films. In brief, this study is a step toward the future development of flexible chemical sensor platforms and beyond.

Cotton, nanoporous cellulose and polyester fabric surfaces are functionalized with combinations of in situ grown silica NPs, polyphenol coating, and protein co-immobilization to enhance surface area, antibody binding efficiency, and biosensing.