P-BINAP-Ru (1100 molFA molRu -1 h -1 ) and P-dppm-Ru (1049 molFA molRu -1 h -1 ) are comparably active, whereas P-dppe-Ru (624 molFA molRu -1 h -1 ) and P-dppp-Ru (770 molFA molRu -1 h -1 ) show only a slightly improved performance, compared to the monodentate P-PPh3-Ru (536 molFA molRu -1 h -1 ). The catalytic results highlight the advantageous properties of bidentate macroligands, which can improve the ligating ability and increase the electron density at the metal center. Other studies on solid molecular catalysts for the CO2 hydrogenation to formate are in agreement with this promoting effect of multidentate ligands. Specifically, Graf et al. and Tai et al. showed that the bite angle of diphosphines, which is determined by the length of their alkyl bridge, is a decisive criterion and that small bite angles of diphosphines lead to active metal phosphine complexes. Moreover, the covalent fixation of the diphosphines in a crosslinked framework must be considered, which reduces the degree of freedom compared to the molecular ligand. As a consequence, the P-dppe and P-dppp are probably not flexible enough to provide a bidentate coordination to the metal center, whereas the spatially close coordination sites of P-dppm ensure the proximity of the bidentate donor sites even in a stiffened skeleton. According to this relation, the structural rigidity of the BINAP and Xantphos ligands, which is reflected in the porosity formed, enables the multidentate coordination of the Ru species, leading to high initial activities in the CO2 hydrogenation to formate. In X-ray photoelectron spectroscopy (XPS), the overlap of the Ru3d peaks with the dominant C1s peak in combination with the low metal loadings unfortunately does not allow an unambiguous electronic specification of the ruthenium species. 75 Regarding the reaction progress and the consecutive recycling runs, the reaction rates of the catalysts decrease as the catalysis proceeds (Fig. ). However, the deactivation is reduced and delayed compared to the monodentate macroligand P-PPh3-Ru, presumably referring to the bidentate coordination environment of the solid diphosphines. P-dppe-Ru and P-dppp-Ru, which probably have spatially separated donor centers, are deactivated in the first run, leading to a significant drop in catalytic productivity between the first and second recycling runs. Subsequently, a nearly constant reaction rate occurs in the last two catalytic runs, with P-dppp-Ru showing higher steady-state productivity than P-dppe-Ru. P-dppm-Ru exhibits the highest productivity of all catalysts in the first run (5191 molFA molRu -1 after 5.5 h), without any relevant deactivation, as the kinetic curve shows a linear increase over the reaction time. A slight deactivation occurs in the second run, followed by a sharp drop in activity from the second to the third run. Hence, it appears that some degradation of the catalyst occurred during the overnight storage of the catalyst between these two recycling runs. A slight decrease of the reaction rate continues in the third and fourth runs. For P-Xantphos, deactivation occurs continuously during the first and second recycling runs, while the catalytic performance stabilizes in the subsequent runs, exhibiting almost similar reaction rates. P-BINAP shows a comparable induction period, although its high steady-state activity is already reached in the second run. Overall, the examination of the catalytic stabilities suggests the superior properties of rigid bidentate macroligands with spatially close diphosphine centers, leading to active and stable catalysts after a certain induction period. In order to consider the changes in catalytic performance over the multiple recycling steps, we have listed the respective productivities in the first and fourth recycling runs for a better comparison (Table ).