Supramolecular recognition on the surface of two-dimensional polyketones

Two-dimensional polymers constitute an emerging class of materials with structurally defined, atomically thin architectures that impart unique optical, electronic, and host-guest properties. Here, we report the synthesis of a crystalline two-dimensional polyketone (2D-PK) via a Friedel-Crafts acylation reaction at a solid-liquid interface on aluminum foil. This interfacial approach yields micrometer-sized sheets composed of highly ordered, stacked layers, as confirmed by SEM, TEM, AFM, and HRTEM analyses. Spectroscopic and diffraction studies-including characteristic shifts in the carbonyl stretching band in IR spectra, sharp solid-state NMR resonances, and well-defined PXRD reflections-further confirm the formation of a crystalline 2D network with an interlayer spacing of 3.54 Å. Beyond structural characterization, 2D-PK exhibits selective supramolecular interactions with organic dyes in aqueous media. Among the investigated analytes, methyl green (MG) shows a markedly stronger affinity for 2D-PK, manifested by pronounced fluorescence enhancement and red-shifted emission, along with distinct changes in NMR, DLS, BET surface area, and UV-Vis absorption profiles. These host-guest interactions arise from a synergistic combination of electrostatic attraction, confinement within polymeric cavities, and charge-transfer-assisted binding, as supported by experimental data and computational simulations. Overall, this study demonstrates that structurally ordered two-dimensional polyketones function as efficient and selective molecular recognition platforms capable of modulating fluorescence responses at low analyte concentrations. These findings highlight the promise of 2D-PKs as versatile materials for chemical sensing, supramolecular chemistry, and future optoelectronic applications.