Scheme 2: Catalyzed hydrogenation of CO2 to formate. To gain a better understanding of the catalytic stability of P-Ru(PPh3)3 and P-PPh3-Ru, recycling experiments were carried out for four consecutive runs, where the catalyst was reused after exchanging the reaction solution (Fig. ). The continuous deactivation described above results in a significant drop in productivity after 5.5 h between the first and second runs. Starting from the third run, the catalysts reach a steady state, while P-Ru(PPh3)3 maintains a slightly higher activity than P-PPh3-Ru. Plausible causes for the observed catalyst deactivation are discussed in the last section of this work. Summarizing the characterization and catalytic data from the comparison of P-Ru(PPh3)3 and P-PPh3-Ru, the method of preparation does not seem to significantly affect the catalytic properties. This outcome is in contrast to the results of Wen et al., who found differences between the post-synthetic metalation and the direct knitting route. They associated the formation of less active metal nanoparticles with the postsynthetic metalation and suggested that direct knitting results in a more active catalyst for the arylsulfonation reaction. Since the different pathways led to barely distinguishable catalysts in the system presented here, we have used the Based on the framework P(2)-PPh3 with incorporated PPh3 donor sites, we immobilized different transition metal precursors by ligand exchange from solution. In the immobilization strategy, a molecular ligand of the metal precursor is exchanged with the fixed phosphine macroligand, while the metal species that do not coordinate to the solid macroligand were separated by filtration. Since several precursors were not completely soluble in methanol, we adapted the solvent and used water or tetrahydrofuran (THF), as appropriate. The metal loadings derived from the XRF analysis reveal that negligible amounts of metal coordinate to the polyphosphine, when the ligand exchange is carried out in the aqueous phase (Fig. ). Referring to the hydrophobic aromatic building units, the poor wettability of the macroligand presumably impedes the accessibility of the coordination sites for the dissolved metal precursor. Consequently, the metal species are not coordinatively bound to the solid framework and remain in the filtrate. In contrast, P(2)-PPh3 readily disperses in methanol The resulting catalysts were evaluated in the CO2 hydrogenation (Fig. ), indicating that the residual coordination environment of the immobilized transition metal has a significant effect on its catalytic performance. promote the activity of Ru and Ir centers, coinciding with studies from the literature. In particular, ligand exchange from the precursors [Ru(p-cymene)Cl2]2 and [Ir(COD)Cl]2 results in active catalysts, while the additional presence of molecular phosphines in (PPh3)3RuCl2 appears to be beneficial for the catalytic application. For the following investigations, the precursor [Ru(pcymene)Cl2]2 was used in the catalyst preparation.