Solid state chemical transformations through ring-opening polymerization of ferrocene-based conjugated microporous polymers in host–guest complexes with benzoxazine-linked cyclodextrin

Abstract

Herein, we describe two ferrocene-derived conjugated microporous polymers (FFCCMPs) prepared through Sonogashira couplings of 9-ferrocenylidene-2,7-dibromo-9H-fluorene (FFC) with tetraethynylpyrene (Py-T) and tetrakis(4-ethynylphenyl)ethene (TPE-T), respectively, and their properties determined using various spectroscopic techniques. These two FFC CMPs formed inclusion complexes (ICs) with a benzoxazine-linked β-cyclodextrin (CD-BZ), with host-guest interactions occurring between the ferrocene and β-CD units. We used Fourier transform infrared spectroscopy, X-ray diffraction, two-dimensional nuclear Overhauser enhancement NMR spectroscopy, solid-state 13C CP/MAS NMR spectroscopy, and thermogravimetric analysis to characterize these FFCCMP/CD-BZ ICs. The BZ units in the FFCCMP/CD-BZ ICs underwent thermal ring-opening polymerization to form new Mannich bridges featuring both intermolecular (OH···O) and intramolecular (OH···N) hydrogen bonds; the resulting TPE-FFCCMP/poly(CD-BZ) and Py-FFCCMP/poly(CD-BZ) ICs exhibited outstanding thermal stability, with the latter having the higher CO2 uptake ability (1.42 mmol g–1) and capacitance (46 F g–1 at 0.5 A g–1).Background: Host–guest complexes formed from macrocyclic hosts possessing hydrophobic cavities such as cyclodextrins (CDs) and various guest molecules have been studied widely for their fascinating characteristics. The interaction of ferrocene-containing CMPs with hydrophobic cavities of CDs to form inclusion complexes materials with excellent thermal properties and these materials can be used in different fields including energy storage and gas capture.Methods: Two ferrocene-based fluorene CMPs—TPE-FFC CMP and Py-FFCCMP—through Sonogashira couplings of 9-ferrocenylidene-2,7-dibromo-9H-fluorene (FFC), as the main block, with tetraethynylpyrene (Py-T) and tetrakis(4-ethynylphenyl)ethene (TPE-T), were successfully synthesized through Sonogashira couplings. Then, the two FFC CMPs were attached to a benzoxazine-functionalized β-cyclodextrin (CD-BZ) through host-guest complexation. The successful synthesis of two FFC CMPs and FFCCMP/CD-BZ ICs was investigated by using Fourier transform infrared spectroscopy, X-ray diffraction, two-dimensional nuclear Overhauser enhancement NMR spectroscopy, solid-state 13C CP/MAS NMR spectroscopy, and thermogravimetric analysis.Significant Findings: The present work offers a new and facile strategy for the preparation CMPs/CD inclusion complexes through supramolecular chemistry and using these materials as an electrode in the energy devices and CO2 uptake.