Structural control of dynamic covalent cages: kinetic thermodynamic assembly and PFAS removal from water.

Dynamic covalent chemistry is a powerful tool to synthesise complex structures from simple building blocks. However, even minor variations in the numerous parameters governing self-assembly can drastically influence the size and structure of the resulting assemblies. Herein, we report the selective formation of three cages belonging to the low-symmetry Tri Tri cage topology for the first time, using highly symmetric tritopic building blocks, confirmed by single-crystal X-ray (SC-XRD) analysis. Fluorinated and non-fluorinated aldehydes were combined with two amines differing in their degree of structural flexibility. Applying either kinetic or thermodynamic control through solvent selection allowed for the selective synthesis of either the low-symmetry Tri Tri or the larger, highly symmetric TriTri assemblies. While the fluorinated linker strongly preferred the formation of the Tri Tri cage topology under thermodynamic control, the non-fluorinated linker selectively formed the TriTri species. Kinetic control, using methanol as a poor solvent, allowed for the selective precipitation of the Tri Tri intermediate. Reduction of the Janus-like fluorinated Tri Tri cages yielded the cages EtF and TRENF , which showed high potential for removing perfluorooctanoic acid (PFOA) from water, with EtF exhibiting structural rearrangements in organic solvents to accommodate PFOA, as observed by H and F NMR titrations in combination with F DOSY measurements.