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Results for “Lewis superacid”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Highly Perfluorinated Covalent Triazine Frameworks Derived from a Low-Temperature Ionothermal Approach Towards Enhanced CO 2 Electroreduction

Perfluorinated covalent triazine frameworks (F-CTFs) have shown unique features and attractive performance in separation and catalysis. However, state-of-art F-CTFs synthesized via the ZnCl 2 -promoted procedure have quite low fluorine contents due to C-F bond cleavage induced by chloride (a Lewis base) and the harsh conditions deployed (400-700 °C). Fabricating F-CTFs with high fluorine contents (> 30 wt%) remains challenging. Herein, we present a low-temperature ionothermal approach (275 °C) to prepare F-CTFs, which is achieved via polymerization of tetrafluoroterephthalonitrile (TFPN) over the Lewis superacids, e.g., zinc triflimide [Zn(NTf 2 ) 2 ] without side reactions. With low catalyst loading (equimolar), F-CTFs are afforded with high fluorine content (31 wt%), surface area up to 367 m 2 g -1 , and micropores around 1.1 nm. The highly hydrophobic F-CTF-1 exhibits good capability to boost electroreduction of CO 2 to CO, with faradaic efficiency of 95.7% at –0.8 V and high current density (–141 mA cm -2 ) surpassing most of the metal-free electrocatalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Low-Temperature Pyrolysis of Aliphatic Polymers Using a Fluorinated Amorphous Silica–Alumina: Cooperative Reactivity between a Redox-Active Radical and an Aluminum Lewis Site

Fluorinated amorphous silica–alumina (F-ASA) prepared by the thermolysis of Krossing’s Al(OC(CF 3 ) 3 ) 3 (PhF) Lewis superacid supported on silica is a very reactive catalyst that promotes the pyrolysis (cracking) of aliphatic polymer melts to produce low molecular weight hyperbranched oils. Initial spectroscopic studies reported previously (Gao, J.; Perras, F. A.; Conley, M. P. J. Am. Chem. Soc . 2025 , 147, 18145–18154) showed that this material contains a distribution of four-, five-, and six-coordinate aluminum sites and a small amount of Brønsted acid sites, similar to typical amorphous silica–alumina materials that are far less reactive in the pyrolysis of aliphatic polymer melts. The objective of this study was to determine whether other active sites present in F-ASA could facilitate pyrolysis reactions. This study provides evidence for the presence of a redox-active silicon oxycarbide persistent radical ((≡Si) 3 C•) in F-ASA. Mims ENDOR EPR experiments show that (≡Si) 3 C• is located close to aluminum. Contacting F-ASA with thianthrene (Th) results in oxidation to form the [Th •+ ][F–ASA] ion-pair, while reactions with 1-hydroxy-2,2,6,6-tetramethylpiperidine (TEMPOH) result in H atom transfer to form TEMPO radical and F-ASA-H containing a mildly acidic (≡Si) 3 C–H. Poisoning studies show that both Lewis acidity and (≡Si) 3 C• are required for polymer pyrolysis reactivity. Finally, we propose that F-ASA promotes the formation of alkyl radicals in polymer melts, which are key intermediates in the thermal pyrolysis reactions of aliphatic polymers, involving the cooperative reactivity of both the Lewis acid and (≡Si) 3 C•.

aluminum↗
DOE OSTI2020

Protonation of CH 3 N 3 and CF 3 N 3 in Superacids: Isolation and Structural Characterization of Long‐Lived Methyl‐ and Trifluoromethylamino Diazonium Ions

Abstract The methylamino diazonium cations [CH 3 N(H)N 2 ] + and [CF 3 N(H)N 2 ] + were prepared as their low‐temperature stable [AsF 6 ] − salts by protonation of azidomethane and azidotrifluoromethane in superacidic systems. They were characterized by NMR and Raman spectroscopy. Unequivocal proof of the protonation site was obtained by the crystal structures of both salts, confirming the formation of alkylamino diazonium ions. The Lewis adducts CH 3 N 3 ⋅AsF 5 and CF 3 N 3 ⋅AsF 5 were also prepared and characterized by low‐temperature NMR and Raman spectroscopy, and also by X‐ray structure determination for CH 3 N 3 ⋅AsF 5 . Electronic structure calculations were performed to provide additional insights. Attempted electrophilic amination of aromatics such as benzene and toluene with methyl‐ and trifluoromethylamino diazonium ions were unsuccessful.

Saal, Thomas↗