Trapping and Releasing of Oxygen in Liquid by Metal-Organic Framework with Light and Heat

Nanoporous materials can adsorb small molecules into their nanospaces. However, the trapping of light gas molecules dissolved in solvents suffers from low concentration and poor adsorption affinity. Here, the reversible trapping and releasing of dissolved oxygen are shown through integrating photosensitization and chemical capturing abilities into a metal-organic framework (MOF), MOMF-1. 9,10-Di(4-pyridyl)anthracene (dpa) ligands in MOMF-1 generates singlet oxygen from triplet oxygen under photoirradiation without additional photosensitizers, and successively reacts with it to produce anthracene endoperoxide, forming MOMF-2, which is proved crystallographically. The reverse reaction also proceeds quantitatively by heating MOMF-2. Moreover, MOMF-1 exhibits excellent water resistance, and completely removes oxygen of ppm order concentrations in water. The new material shown in this report allows controlling of the amount of dissolved oxygen, which can be applicable in various fields relating to numerous oxidation phenomena.

Metal-Organic Frameworks for Practical Separation of Cyclic and Linear Polymers

The purification step in the manufacturing of cyclic polymers is difficult as complete fractionation to eliminate linear impurities requires considerable effort. Here, we report a new polymer separation methodology that uses metal-organic frameworks (MOFs) to discriminate between linear and cyclic polyethylene glycols (PEGs) via selective polymer insertion into the MOF nanopores. Preparation of a MOF-packed column allowed analytical and preparative chromatographic separation of these topologically distinct pairs. In addition, gram-scale PEGs with only cyclic structures were successfully obtained from a crude reaction mixture by using MOF as an adsorbent.

Synthesis of poly(N-isopropylacrylamide) polymer crosslinked with an AIE-active azonaphthol for thermoreversible fluorescence

A fluorescent polymer was synthesized using N-isopropylacrylamide (NIPAM) crosslinked with a divinylazonaphthol monomer via radical emulsion polymerization. Because the crosslinked polymer contained an aggregation-induced emissive (AIE) azonaphthol-based crosslinker, a thermoreversible sol-gel transformation and gelation-induced reversible fluorescence alteration were successfully attained in an aqueous medium. Like typical PNIPAM, the size and transmittance of the polymer dramatically decreased near the lower critical solution temperature (LCST, 36 °C). Such gelation facilitated aggregation of the polymer chains, resulting in the close contact between azonaphthol groups producing fluorescence. The crosslinked polymer exhibited changes in dual properties: one is related to PNIPAM structural alteration, which corresponds to conventional swelling/shrinkage behavior; and the other is involved in the reversible fluorescence change in response to the swelling/shrinkage. Because the major backbone of the polymer was composed of NIPAM with an LCST at 36 °C, the resultant polymer is expected to have potential applications in biologically related fields.