Exclusive formate formation via low-temperature CO2 hydrogenation over a heterogenized iridium pincer catalyst

초록

Carbon capture and utilization via CO2 hydrogenation to formate is a promising strategy for sustainable carbon management, but achieving high catalytic performance under mild, low-temperature conditions remains challenging for heterogeneous systems despite the thermodynamic and operational advantages of low-temperature operation. To overcome this limitation, we designed a heterogenized Ir-PNP pincer catalyst to translate the low-temperature reactivity of molecular Ir pincer motifs into a recyclable porous polymer platform. An iridium-based porous organometallic polymer, IrCl3(PhPNHP)-POMP, was synthesized through Friedel-Crafts polymerization of a molecular IrH2Cl(PhPNHP) precursor. The resulting material features a microporous architecture with a surface area of 470 m2 g-1 and an Ir loading of 19.9 wt%, with Ir(iii) active sites uniformly distributed throughout the polymer matrix. Catalytic evaluation under base-assisted CO2 hydrogenation conditions (H2/CO2 = 1 : 1, 80 bar, triethylamine/H2O) demonstrates that IrCl3(PhPNHP)-POMP shows higher catalytic activity under low-temperature conditions than a previously reported Ru-based heterogeneous pincer catalyst with state-of-the-art performance. Notably, the catalyst enabled formate accumulation up to 3.0 M at 60 degrees C, corresponding to an acid-to-amine ratio of unity. IrCl3(PhPNHP)-POMP exhibits excellent recyclability over seven consecutive cycles without significant activity loss or Ir leaching, confirming robust structural integrity under repeated reaction conditions.

키워드