We provide the first observation and characterization of super electrophilic metal cations on a solid support. For Pd/SSZ-13, the results of our combined experimental (Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, high-angle annular dark-field scanning transmission electron microscopy) and density functional theory study reveal that Pd ions in zeolites, previously identified as Pd+3 and Pd+4, are, in fact, present as super electrophilic Pd+2 species (charge-transfer complex/ion pair with the negatively charged framework oxygens). In this contribution, we reassign the spectroscopic signatures of these species, discuss the unusual coordination environment of “naked” (ligand-free) super electrophilic Pd+2 in SSZ-13, and their complexes with CO and NO. With CO, nonclassical, highly positive [Pd­(CO)2]2+ ions are formed with the zeolite framework acting as a weakly coordinating anion (ion pairs). Nonclassical carbonyl complexes also form with Pt+2 and Ag+ in SSZ-13. The Pd+2(CO)2 complex is remarkably stable in zeolite cages even in the presence of water. Dicarbonyl and nitrosyl Pd+2 complexes, in turn, serve as precursors to the synthesis of previously inaccessible Pd+2–carbonyl–olefin [Pd­(CO)­(C2H4)] and Pd+2–nitrosyl–olefin [Pd­(NO)­(C2H4)] complexes. Overall, we show that the zeolite framework can stabilize super electrophilic metal (Pd) cations and show the new chemistry of the Pd/SSZ-13 system with implications for adsorption and catalysis.

The catalytic sites of acidic zeolite are profoundly altered by the presence of water changing the nature of the Brønsted acid site. High-resolution solid-state NMR spectroscopy shows water interacting with zeolite Brønsted acid sites, converting them to hydrated hydronium ions over a wide range of temperature and thermodynamic activity of water. A signal at 9 ppm was observed at loadings of 2–9 water molecules per Brønsted acid site and is assigned to hydrated hydronium ions on the basis of the evolution of the signal with increasing water content, chemical shift calculations, and the direct comparison with HClO4 in water. The intensity of 1H–29Si cross-polarization signal first increased and then decreased with increasing water chemical potential. This indicates that hydrogen bonds between water molecules and the tetrahedrally coordinated aluminum in the zeolite lattice weaken with the formation of hydronium ion–water clusters and increase the mobility of protons. DFT-based ab initio molecular dynamics studies at multiple temperatures and water concentrations agree well with this interpretation. Above 140 °C, however, fast proton exchange between bridging hydroxyl groups and water occurs even in the presence of only one water molecule per acid site.

The majority of harmful atmospheric CO and NO x emissions are from vehicle exhausts.A lthough there has been success addressing NO x emissions at temperatures above 250 8 8Cw ith selective catalytic reduction technology,e missions during vehicle cold start (when the temperature is below 150 8 8C), are am ajor challenge.H erein, we showw ec an completely eliminate both CO and NO x emissions simultaneously under realistic exhaust flow, using ah ighly loaded (2 wt %) atomically dispersed palladium in the extra-framework positions of the small-pore chabazite material as aC O and passive NO x adsorber.U ntil now,a tomically dispersed highly loaded (> 0.3 wt %) transition-metal/SSZ-13 materials have not been known. We devised ag eneral, simple,a nd scalable route to prepare such materials for Pt II and Pd II . Through spectroscopyand materials testing we showthat both CO and NO x can be simultaneously completely abated with 100 %e fficiency by the formation of mixed carbonyl-nitrosyl palladium complex in chabazite micropore.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.