Metalloligand-anion frameworks: Tunable polarized luminescence and crystal-to-crystal transformation

Progress and potentialThe syntheses of the widely studied porous molecular materials, including MOFs and COFs, sometimes suffer from harsh hydrothermal conditions and long reaction times. A type of 3D metalloligand-anion framework with a hexagonal or rectangular pore, based on the intralayer F···H hydrogen bonding interaction and interlayer cation-anion electrostatic interactions, is presented here by simple polymorphic crystallization of an ionic iridium complex. The obtained microcrystals display linearly polarized blue phosphorescence with a polarization degree of up to 0.91. Furthermore, these crystals undergo a crystal-to-crystal transformation to afford another polymorphic crystal with included chiral solvent molecules to show circularly polarized luminescence with a dissymmetry factor of 0.1. This work demonstrates a unique and simple concept to obtain polymorphic porous molecular materials with prominent optical properties.Highlights•Porous materials constructed by hydrogen-bonding and electrostatic interactions•Linearly polarized luminescence with a polarization degree of up to 0.9•Polymorphic assembly by a crystal-to-crystal transformation•Circularly polarized phosphorescence with a dissymmetry factor of 0.1SummaryNoncovalent organic frameworks (NCOFs) are porous materials constructed by diverse intermolecular interactions. It is challenging to obtain polymorphic NCOFs with adjustable pores and high-performance polarized luminescence. Here, two polymorphic organometallic NCOFs, 1-α and 1-β, are presented from an iridium complex 1 based on the intralayer F···H hydrogen bonding and interlayer cation-anion electrostatic interactions. These metalloligand-anion frameworks display linearly polarized blue phosphorescence with a polarization degree of up to 0.91 and optical waveguide properties. The 1-α microcrystals doped with a ruthenium acceptor manifest a reversible response to Et2O vapor, showing modulated energy transfer and polarized luminescence. The 1-α and 1-β microcrystals are transformed into another polymorphic 1-γ crystal by incorporating chiral (R/S)-carvone guests, affording tunable circularly polarized luminescence with a dissymmetry factor of around 0.1. This work provides a unique concept to obtain polymorphic NCOFs, demonstrating prominent potential in multifunctional optical and chiroptical applications.Graphical abstract