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The first example of photocatalytic trifluoromethoxylation of arenes and heteroarenes under continuous-flow conditions is described. Application of continuous-flow microreactor technology allowed to reduce the residence time up to 16 times in comparison to the batch procedure, while achieving similar or higher yields. In addition, the use of inorganic bases was demonstrated to increase the reaction yield under batch conditions.
All fluorochemicals—including elemental fluorine and nucleophilic, electrophilic, and radical fluorinating reagents—are prepared from hydrogen fluoride (HF). This highly toxic and corrosive gas is produced by the reaction of acid-grade fluorspar (>97% CaF
2
) with sulfuric acid under harsh conditions. The use of fluorspar to produce fluorochemicals via a process that bypasses HF is highly desirable but remains an unsolved problem because of the prohibitive insolubility of CaF
2
. Inspired by calcium phosphate biomineralization, we herein disclose a protocol of treating acid-grade fluorspar with dipotassium hydrogen phosphate (K
2
HPO
4
) under mechanochemical conditions. The process affords a solid composed of crystalline K
3
(HPO
4
)F and K
2−
x
Ca
y
(PO
3
F)
a
(PO
4
)
b
, which is found suitable for forging sulfur-fluorine and carbon-fluorine bonds.
Aiming at knowledge‐driven design of novel metal–ceria catalysts for automotive exhaust abatement, current efforts mostly pertain to the synthesis and understanding of well‐defined systems. In contrast, technical catalysts are often heterogeneous in their metal speciation. Here, we unveiled rich structural dynamics of a conventional impregnated Pd/CeO2 catalyst during CO oxidation. In situ X‐ray photoelectron spectroscopy and operando X‐ray absorption spectroscopy revealed the presence of metallic and oxidic Pd states during the reaction. Using transient operando infrared spectroscopy, we probed the nature and reactivity of the surface intermediates involved in CO oxidation. We found that while low‐temperature activity is associated with sub‐oxidized and interfacial Pd sites, the reaction at elevated temperatures involves metallic Pd. These results highlight the utility of the multi‐technique operando approach for establishing structure–activity relationships of technical catalysts.
Operando spectroscopy captures the dynamic behavior of ceria‐supported Pd single atoms, clusters, and nanoparticles during CO oxidation. In their Research Article (e202200434), Emiel J. M. Hensen et al. elucidate the catalytic role of different Pd species using a combination of in situ spectroscopy with transient and steady‐state kinetic analysis. Highly dispersed Pd–oxo species and interfacial Pd sites catalyze low‐temperature CO oxidation, while metallic Pd contributes to the activity at elevated temperature.
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