Light and Guest Responsive Behavior in a Porous Coordination Network Enabled by Reversible [2+2] Photocycloaddition

Mei Yan Gao, Lunjie Liu, Chenghua Deng, Volodymyr Bon, Bai Qiao Song, Sihai Yang, Martin Schröder, Stefan Kaskel, Michael J. Zaworotko

Research output: Contribution to journalArticlepeer-review

Abstract

Stimuli-responsive physisorbents that undergo reversible structural transformations induced by external stimuli (e.g. light, guests, or heat) offer the promise of utility in gas storage and separation. Whereas reports on guest or light-responsive sorbents have increased in recent years, we are unaware of reports on sorbents that exhibit both light and guest-induced structural transformations. Herein, we report that the square lattice, sql, topology coordination network Zn(fba)(bis) ⋅ 2DMF (sql-5,6-Zn-α, 5=trans-4,4′-bis(1-imidazolyl)stilbene=bis, 6=2,2-bis(4-carboxyphenyl)hexafluoropropane=H2fba) underwent single-crystal-to-single-crystal transformation (SCSC) upon activation, affording nonporous sql-5,6-Zn-β. Parallel alignment at 3.23 Å of olefinic moieties on adjacent bis ligands in sql-5,6-Zn-α enabled SCSC [2+2] photocycloaddition upon exposure to UV light (365 nm) or sunlight. sql-5,6-Zn-α thereby transformed to mot-5,6-Zn-α, which was subsequently activated to the narrow pore phase mot-5,6-Zn-β. sql-5,6-Zn-β and mot-5,6-Zn-β both exhibited S-shaped adsorption isotherms characteristic of guest-induced structural changes when exposed to CO2 at 195 K (type-F–IV and type F–I, respectively). Cycling experiments conducted upon sql-5,6-Zn-β reduced particle size after cycle 1 and induced transformation into a rare example of a shape memory coordination network, sql-5,6-Zn-γ. Insight into this smorgasbord of SCSC phase changes was gained from in situ PXRD, single crystal XRD and 1H NMR spectroscopy experiments.

Original languageEnglish
Article numbere202404084
JournalAngewandte Chemie - International Edition
Volume63
Issue number34
DOIs
Publication statusPublished - 19 Aug 2024

Keywords

  • flexibility
  • photocycloaddition
  • porous coordination networks
  • shape memory
  • single-crystal-to-single-crystal transformation

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