Fourier-transform infrared spectroscopy (FTIR) (Fig. ) proves the existence of aliphatic C-Hvibrations (2800 cm -1 -2980 cm -1 ), presumably originating from methylene bridges between the aromatic units. The aromatic C-H-vibration (3000 cm -1 -3080 cm -1 ), the vibration modes of the aromatic ring skeleton (1450 cm -1 -1730 cm -1 ), the C-N-vibration (1315 cm -1 ) and the characteristic bending vibrations of the aromatic system (701 cm -1 -814 cm indicate the presence of partially crosslinked FDA moieties with unreacted methoxy groups, coinciding with the respective HCP yields, which exceed the ones from an ideally crosslinked skeleton (Table ). pBz (1103 m 2 g -1 (BET)) and pNPh3 (802 m 2 g -1 (BET)) exhibit a micro-and mesoporosity (Fig. ). Nitrogen physisorption measurements illustrate a distinct, non-closing hysteresis, which is known for non-rigid materials and can be attributed to capillary condensation, pore blocking and swelling effects. However, no insoluble product is obtained through the crosslinking of the monomer PPh3 (III) under similar reaction conditions (Scheme 1). This reactivity gap can be associated to the binding of the monomeric heteroatoms to FeCl3, withdrawing electron density from the aromatic rings.