Bulk Post-Polymerization Modification of a Single-Crystalline 2D Polymer via the Katritzky Reaction: A Modular Platform for Functional 2D Materials
Year: 2026
Type: preprint
Abstract: Synthesizing two-dimensional polymers (2DPs) via single-crystal-to-single-crystal (SCSC) topochemical polymerization presents a dual challenge: preorganizing multifunctional monomers into two-dimensional crystal lattices and ensuring their polymerizable groups remain in close proximity to enable topochemical reaction in 2D. Consequently, topochemical 2DPs remain rare, and strategies for their post-polymerization modification, a standard tool in 1D polymer chemistry, are even more limited. Existing pyrylium-functionalized 2DPs suffer from severe steric hindrance caused by 2,6-di-tert-butyl substituents on pyrylium, restricting their post-synthetic Katritzky transformations solely to small nucleophiles like ammonia. To overcome this limitation, we synthesized a 2,6-di(isopropyl)styrylpyrylium triolefin monomer featuring 2,6-di-isopropyl substituents on pyrylium instead of 2,6di-tert-butyl. This subtle steric modification preserves topochemical polymerizability, while dramatically enhancing the reactivity of the resulting 2DP, enabling facile pore-wall functionalization with nucleophiles such as methylamine or ethylenediamine, to form Nmethyl- and N-(2-aminoethyl)pyridinium sites, respectively. Spectroscopic measurements show no detectable residual pyrylium in either derivative, while the ion-exchange capacity of the N-methyl derivative agrees with its theoretical capacity. These results establish solid-state pyrylium-to-pyridinium conversion as a strategy for post-polymerization modification of a topochemical 2DP precursor and represent a solid foundation for accessing a wide variety of topochemical 2DPs with engineered pore functionality.
Source: ChemRxiv
Institutions: ETH Zurich, Empa, University of Fribourg
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7215100331