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[This retracts the article DOI: 10.1021/jacsau.2c00402.].

Electrochemical polarization, which often plays a critical role in driving chemical reactions at solid-liquid interfaces, can arise spontaneously through the exchange of ions and/or electrons across the interface. However, the extent to which such spontaneous polarization prevails at nonconductive interfaces remains unclear because such materials preclude measuring and controlling the degree of interfacial polarization via standard (i.e., wired) potentiometric methods. Herein, we circumvent the limitations of wired potentiometry by applying infrared and ambient pressure X-ray photoelectron spectroscopies (AP-XPS) to probe the electrochemical potential of nonconductive interfaces as a function of solution composition. As a model class of macroscopically nonconductive interfaces, we specifically probe the degree of spontaneous polarization of ZrO2-supported Pt and Au nanoparticles immersed in aqueous solutions of varying pH. Shifts in the Pt-adsorbed CO vibrational band position evince electrochemical polarization of the Pt/ZrO2-water interface with changing pH, and AP-XPS reveals quasi-Nernstian shifts of the electrochemical potential of Pt and Au with pH in the presence of H2. These results indicate that spontaneous proton transfer via equilibrated H+/H2 interconversion spontaneously polarizes metal nanoparticles even when supported on a nonconductive host. Consequently, these findings indicate that solution composition (i.e., pH) can be an effective handle for tuning interfacial electrical polarization and potential at nonconductive interfaces.

The archetypal silica- and aluminosilicate-based zeolite-type materials are renowned for wide-ranging applications in heterogeneous catalysis, gas-separation and ion-exchange. Their compositional space can be expanded to include nanoporous metal chalcogenides, exemplified by germanium and tin sulfides and selenides. By comparison with the properties of bulk metal dichalcogenides and their 2D derivatives, these open-framework analogues may be viewed as three-dimensional semiconductors filled with nanometer voids. Applications exist in a range of molecule size and shape discriminating devices. However, what is the electronic structure of nanoporous metal chalcogenides? Herein, materials modeling is used to describe the properties of a homologous series of nanoporous metal chalcogenides denoted np-MX2, where M = Si, Ge, Sn, Pb, and X = O, S, Se, Te, with Sodalite, LTA and aluminum chromium phosphate-1 structure types. Depending on the choice of metal and anion their properties can be tuned from insulators to semiconductors to metals with additional modification achieved through doping, solid solutions, and inclusion (with fullerene, quantum dots, and hole transport materials). These systems form the basis of a new branch of semiconductor nanochemistry in three dimensions.

We report the continuous, gas-phase synthesis of α-methylene-δ-valerolactone (MVL) from δ-valerolactone (DVL) and formaldehyde (FA) over alkaline earth oxide catalysts. MgO, CaO, and BaO supported on silica (∼5 wt%) were active for MVL production (613 K, 0.4 kPa DVL, 1.2 kPa FA, 101 kPa total pressure). CaO and BaO showed 90% and 83% selectivity to MVL at ∼60% DVL conversion, respectively. Decreasing contact times improved MVL selectivity for all three catalysts, achieving near quantitative selectivity at DVL conversions <40% with CaO. Further studies with CaO indicated that increasing the FA partial pressure for a given DVL partial pressure negligibly changed conversion while maintaining high selectivity; however, increasing the reaction temperature generally resulted in lower MVL selectivity. Deactivation and carbon loss were attributed to non-volatile compound formation from series and parallel reactions that consume MVL and DVL and poison the catalyst surface. These side reactions were more pronounced at high temperatures and higher contact times. While slow deactivation poses a challenge, the catalyst could be fully regenerated by calcining at 773 K for 4 h under flowing air. As the product mixture of MVL and DVL is difficult to separate, we developed a selective polymerization strategy to convert either one or both monomers into valuable polymeric materials, thereby achieving efficient separation and concurrent polymer production. Using a model mixture of 30 wt% of MVL in DVL, vinyl-addition polymerization converted MVL to the corresponding vinyl polymer (PMVL)VAP in 98% yield, while DVL was recovered in 96% yield by distillation. Alternatively, ring-opening polymerization of the same mixture resulted in a DVL/MVL copolyester and separatable vinyl homopolymer P(MVL)VAP. [ABSTRACT FROM AUTHOR]

Sn-BEA zeolite is known to catalyze the aldose-to-ketose isomerization of xylose and glucose; however, the selectivity to pentose and hexose isomers is not stoichiometric, suggesting the formation of other products. In the present study, we have observed near-complete conversion of all pentose and hexose isomers when xylose and glucose were reacted in the presence of Sn-BEA at 140 °C and 200 °C, respectively. The previously unidentified products were identified by nuclear magnetic resonance and mass spectrometry to be hydroxyalkanoic acids and their derivatives. The hydroxyl-rich acids comprise a significant fraction of the converted sugars and are potential monomers for the synthesis of hyper-crosslinked, biodegradable polymers.