Creation of Heterogeneous Single-Site Catalysts for RWGS Reaction: Ruthenium Complex on Porous Ionic Polymers via Electrostatic Interactions.

Heterogeneous single-metal-site catalysts (HSMSCs) have been recognized as promising materials due to the advantages of evenly distributed active metal sites, easy separation, and recyclability. Herein, we construct a single-site Ru catalyst on porous ionic polymers (Ru/PIPs-IL3) via electrostatic interactions, which is a practical and useful strategy for synthesizing HSMSCs. The strong electrostatic interactions (ΔH = -73.4 and -83.5 kJ/mol for Ru-PPh4 and Ru-P(vBn)(vPh)3, respectively) between the quaternary phosphonium cations and oxygen anions of the cyclopentadienyl ligand in Ru species were both consolidated by DFT calculation and X-ray crystallography. The XPS, ATR-IR, HAADF-STEM, and EXAFS analyses and ion exchange experiment were employed to characterize the structure of Ru/PIPs-IL3. These results provide compelling evidence that PIPs-IL3 can interact with Shvo's catalyst in a manner analogous to that observed with quaternary phosphonium (PPh4Cl), thereby anchoring the Ru through electrostatic interactions. Such heterogeneous single-site Ru catalyst Ru/PIPs-IL3 exhibited a twofold activity compared to the homogeneous catalyst with a TONCO of up to 545 and an excellent 98.5% CO selectivity in the low-temperature reverse water-gas shift reaction.