An effective heterogeneous Ir(III) catalyst, immobilized on a heptazine-based organic framework, for the hydrogenation of CO2 to formate

• Heterogenized Ir(III) catalysts were prepared by immobilization of the {IrCp*} motif on heptazine-based COF.
• Loading amount of Ir ions on COF reaches to ca. 0.86 wt%.
• Heterogeneous catalyst exhibits high CO2 hydrogenation activity.
• Catalytic efficiency is maintained over repeated recycling.

Heterogenized Ir(III) catalysts were synthesized through the formation of coordination bonds between Ir(III) ions and heptazine-based covalent organic frameworks (COFs). The coordination environment of the Ir(III) ion contained the two heptazinyl nitrogen atoms as well as Cp* and Cl− anions. The heterogeneous catalyst exhibits high CO2 hydrogenation activity (turnover number (TON) = 6400 and turnover frequency (TOF) = 1500 h−1). In addition, the sub-micron sized catalyst was easily separated by filtration and the catalytic efficiency of the isolated catalyst was demonstrated over repeated cycles.

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