The presence of C-P vibrations (1435 cm -1 ) in the macroligands coincides with the detection of phosphorus in the XRF analysis (Table ). Regarding the involvement of monomeric phosphine units, the actual nature of the phosphine fixation in the skeleton remains inexplicit. Whilst the use of FeCl3 does not allow the knitting of sole PPh3 with FDA (Scheme 1), it cannot be stated, whether the phosphine units in Fe-P-BP-Ru are chemically bound to the aromatic framework or if their presence is due to physical entrapment effects inside the framework, which consists out of selfcrosslinked biphenyl crosslinkers. In contrast to Fe-P-BP-Ru (50 % yield, w(P) = 0.67 wt%) and SA-P-BP-Ru (42 % yield, w(P) = 0.20 wt%), the use of AlCl3 is accompanied by an extended polymer yield (79 %) and an almost doubled phosphorus content (1.1 wt%), resulting from the enhanced activation of the crosslinking reagents. The ruthenium uptake of the respective phosphine centers is identical for Al-P-BP-Ru and Fe-P-BP-Ru (4:1), whereas a lower P:Ru ratio of 2.5:1 is obtained for SA-P-BP-Ru. This improved ligating ability may be related to a beneficial accessibility of the the phosphine ligands, as drastically enlarged porous structures of Fe-P-BP and SA-P-BP are revealed by nitrogen physisorption (Fig. ). The significant differences in porosity can be associated to the proportion of crosslinked PPh3 units and ethylene linkers from the activation of DCE in Al-P-BP. This augmented incorporation of flexible units diminishes the rigidity of the framework and facilitates the denser packing of the polymer. Our findings agree with the variation of the Lewis acids for the crosslinking of aromatic polymers in the study of Ahn Water vapor sorption (Fig. ) draws some insights into the affinity of the formed polyphosphines towards water. It indicates the hydrophobicity of the HCPs, consisting of nonpolar aromatic units, but also proves a certain wettability with water. Fe-P-BP shows a water uptake at p/p0 = 0.45, which occurs at lower relative pressures compared to Al-P-BP and SA-P-BP. The enhanced fraction of chlorine residues presumably promotes the adsorption of water molecules in the framework, whose later nucleation causes an increasing uptake of water at higher partial pressures.