Studies On Photocatalytic Properties Of Pyrene-based Metal-Organic Framework NU-1000

Atom transfer radical addition reaction（ATRA）can effectively construct perfluoro groups into olefin substrates.ATRA reaction has the following characteristics:The reaction has highly atom economy,the reaction has a wide range of substrate applications and the reaction is effective constructing carbon-carbon bond,carbon-halogen bond in a single strike.However,in comparison to the facile generation of alkyl radical from the substrates and the relatively negative oxidation potentials and the generally needed large enough over-potential of common perfluoroalkyl radical precursors perfluoroalkyl iodides made it in the presence of photoresponsive Ru/Ir multipyridyl complexes.Partially fluorinated arenes are highly prized molecules in pharmaceutical and agricultural chemistry,and in materials science.In recognition of the need for more facile access to partially fluorinated arenes have received considerable attention.In order to avoid the preparation of partially fluorinated arenes through difficult multiple prefunctionalizations,people have passed the prefunctionalized arenes undergoes a selective hydrodefluorination reaction to obtain a target molecule,which is relatively difficult due to the characteristics of the C-F bond.Due to the good visible-light harvesting,powerful triplet photosensitising ability,excellent energy transfer properties and large and stable aromatic ring structure,the pyene-based metal-organic frameworks NU-1000 is a kind of photocatalyst with excellent performance.The application of NU-1000 in the above issues is discussed in this paper.（1）Utilizing the energy transfer property of NU-1000 and circumventing the severe dependency of the PET-induced heterolytic cleavages on reduction potentials of photocatalysts,the aliphatic terminal alkenes bearing hydrophilic hydroxyl or hydrophobic phenyl/phenoxy substituents on the other ends of olefins were smoothly transformed into the corresponding difunctionalized products in moderate to high yields（67%-93%）.Mechanistic studies have shown that the reaction follows the EnT-mediated mechanism of free radical reaction.This is the first organic conversion using the photoinduced EnT process of MOFs rather than the photooxidation process.The application of this photocatalytic strategy was further expended to ATRA of aliphatic and aromatic terminal alkynes,the corresponding ratios of（Z）-/（E）-isomers（73:27）were higher than most of the reported results in literatures（54:46）.When employing conjugated arylalkenes as substrates,the photocatalytic ATRA reaction,the HI elimination of the ATRA product,and the EnT-mediated（E）/（Z）-isomerisation could be merged together in one-pot to afford highly（Z）-selective perfluoroalkyl styrenes.The reaction is also applicable to biomolecules such as estrone derivatives.（2）Utilizing the largeπconjugated property of NU-1000,the problem of strong coordination between C-F bond and catalyst-F bond was solved in the methord of photoelectron transfer,and the photocatalytic HDF reaction of perfluoroarene was realized.The reaction yield is closely related to the geometry of the Perfluoroarenes.When the octafluoronaphthalene was used as the substrate,the catalysis system even undergo di-HDF events to afford products.When cyclohexene was put into the reaction,we obtained a C-F reductive alkylation product.Mechanistic studies have shown that the system followed the HDF reaction mechanism mediated by the outer electron transfer.The IR spectrum of NU-1000 suspension upon addition of C₆F₆ was further proved that“π-π”interaction has a very important effect on substrates activation.