title: A Photoresponsive Smart Covalent Organic Framework.
abstract: Ordered π-columnar structures found in covalent organic frameworks (COFs) render them attractive as smart materials. However, external-stimuli-responsive COFs have not been explored. Here we report the design and synthesis of a photoresponsive COF with anthracene units as the photoresponsive π-building blocks. The COF is switchable upon photoirradiation to yield a concavo-convex polygon skeleton through the interlayer [4π+4π] cycloaddition of anthracene units stacked in the π-columns. This cycloaddition reaction is thermally reversible; heating resets the anthracene layers and regenerates the COF. These external-stimuli-induced structural transformations are accompanied by profound changes in properties, including gas adsorption, π-electronic function, and luminescence. The results suggest that COFs are useful for designing smart porous materials with properties that are controllable by external stimuli.
authors.affiliation: Department of Materials Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787 (Japan).
authors.forename: Ning
authors.initials: N
authors.lastname: Huang
authors.affiliation: Department of Materials Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787 (Japan).|Present address: National Center of Nanoscience and Technology, No.11 ZhongGuanCun, BeiYiTiao, Beijing, 100190 (China).
authors.forename: Xuesong
authors.initials: X
authors.lastname: Ding
authors.affiliation: Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, KAIST, Daejeon 305-701 (Republic of Korea).
authors.forename: Jangbae
authors.initials: J
authors.lastname: Kim
authors.affiliation: Center for Nanomaterials and Chemical Reactions, Institute for Basic Science, KAIST, Daejeon 305-701 (Republic of Korea).
authors.forename: Hyotcherl
authors.initials: H
authors.lastname: Ihee
authors.affiliation: Department of Materials Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki 444-8787 (Japan). jiang@ims.ac.jp.
authors.forename: Donglin
authors.initials: D
authors.lastname: Jiang
keywords: anthracene; covalent organic frameworks; photoresponsive materials; porous polymer; smart materials