Heterogeneous immobilized molecular catalysis has gained significant attention as a platform for creating more efficient and selective catalysts. A promising type of immobilized molecular catalysts are made from porous organic polymers (POPs) due to their high stability, porosity, and ability to mimic the catalytic activity and selectivity of homogeneous organometallic catalysts. These properties of the POP‐based systems make them very attractive as heterogeneous catalysts for hydrogenation of CO 2 to formate, where predominately homogeneous systems have been applied. In this study, five POPs were synthesized and assessed in the hydrogenation of CO 2 where the active catalysts were made in‐situ by mixing IrCl 3 and the POPs. One of the Ir/POP catalysts provided a turn‐over number (TON) >20,000, which is among the highest for POP‐based systems. Thorough characterization (CO 2 ‐ and N 2 ‐physisorption, TGA, CHN‐analysis, XRD, XPS, SEM, STEM and TEM) was performed. Notably, the developed Ir/POP system also showed catalytic activity for the decomposition of formic acid into H 2 enabling the use of formic acid as a renewable energy carrier.