Regarding the loss of activity in the recycling experiments, the structural alterations of the catalysts are analyzed. For an in-depth study of a selected catalyst, we refer to the detailed investigation of P-Xantphos. Since we intend to compare the macroligand effects of a wider range of coordination environments in this work, we have not focused on a specific catalyst here. The XRF analysis of the filtrates after the first catalytic runs reveal that only negligible amounts of Ru leached into the reaction solutions (< 0.0015 % of the immobilized Ru amount) (Table ). In addition, we carried out an exemplary hot leaching experiment with P-BINAP-Ru, where the catalyst was removed from the hot reaction solution after 2 h, the remaining solution was again pressurized with CO2 and H2 and the reaction was continued in the absence of the solid catalyst (Fig. ). Subsequently, no further formate formation was observed. Hence, the leaching of the active species into the liquid phase can be excluded as the origin of catalyst deactivation, proving the heterogeneous nature of the catalysts. FTIR measurements of the pristine and spent catalysts illustrate the structural alterations of the respective catalysts over four recycling runs (Fig. ). Especially P-PPh3-Ru and P-dppp-Ru seem to undergo modifications of the alkyl bridges, as a distinct peak of the aliphatic C-H vibrations (2982 cm -1 ) appears after catalysis. This alteration is probably related to a change in the porous structure, which has been described for HCPs under catalytic conditions. However, it has been shown that a possible loss of HCP porosity does not play a significant role in the initial decrease in catalytic activity. Accordingly, the non-porous macroligands reported here still show high catalytic activities, which is related to their swelling ability in the solvated state. Therefore, it is suggested, that pore-blocking effects or porosity collapse are not the major causes for the deactivation. In the IR spectra of P-dppm-Ru, P-dppe-Ru and P-dppp-Ru, new peaks appear at 1918 cm -1 (P-dppm-Ru) and 1928 cm -1 (P-dppe-Ru, P-dppp-Ru) after catalysis. These vibrational modes can most likely be assigned to carbonyl ligands, bound to Ru species. Strongly coordinating carbon monoxide has been shown to poison most of the molecular phosphine metal complexes and is considered to cause the deactivation of heterogenized Ru phosphine catalysts. Hence, the formation of bound carbonyl ligands and the resulting change in the Ru complex seems to be responsible for the deactivation of the solid catalysts. It cannot be determined, whether this poisoning is not pronounced for P-Xantphos-Ru and P-BINAP-Ru or whether the presence of coordinating carbonyl ligands cannot be detected due to the lower amount of Ru sites.