Imidazolium-Derived Porous Organic Polymer as Robust Platform for Rhodium-Catalyzed N₂O Hydrogenation and Alcohol...

The catalytic conversion of nitrous oxide, a potent greenhouse gas and ozone-depleting substance, offers a promising strategy for mitigating emissions but requires efficient catalysts that operate under mild conditions. Here, a porous organic polymer was designed as a functional platform for accommodating built-in catalytic sites. The polymer incorporates rigid 1,3-dimethylbenzimidazolium iodide units as stable precursors to N-heterocyclic carbenes, providing suitable coordination sites to molecular catalysts, high surface area, and chemical robustness. Deprotonating these precursors generates free carbene ligands that effectively coordinate and immobilize a rhodium bis(olefin) amine complex. Upon activation with base, the air stable immobilized complex forms reactive metal-ligand cooperative Rh-N sites that convert nitrous oxide to nitrogen via in situ generated rhodium(I) hydride species. Exceptional performance was observed during catalytic hydrogenation of nitrous oxide under heterogeneous solid-liquid-gas conditions in batch reactors (using tetrahydrofuran or water) and under solid-gas conditions. Furthermore, the catalyst enabled the dehydrogenative coupling of primary alcohols (methanol, ethanol and benzyl alcohol) with nitrous oxide as a hydrogen acceptor, achieving turnover numbers that surpass all previously reported catalysts. These findings demonstrate the potential of porous organic polymer-metal complexes as robust, recyclable and efficient catalysts.