The catalytic hydrogenolysis of compounds derived from guaiacol on the Cu (111) surface: mechanisms from DFT studies.

Pyrolysis oils have inferior properties compared to liquid hydrocarbon fuels, owing to the presence of oxygenated compounds such as guaiacol, C6H4(OH)(OCH3). The catalytic hydro-deoxygenation (HDO) of phenolic compounds derived from guaiacol, i.e. catechol, phenol and anisole were investigated over the Cu (111) surface to unravel the elementary steps involved in the process of bio-oil upgrade. The phenolic compounds adsorb through their π systems to the surface, where steric effects of the methoxy group reduce the stability of anisole on the surface. To produce benzene, hydroxyl removal from catechol and phenol occurs in a stepwise fashion, where dehydroxylation of catechol is more challenging than phenol. Thermodynamically, catechol is the preferred oxygenated product, but it is the most challenging to transform to benzene, requiring an energy barrier of 1.8 eV to be overcome, which is similar to the HDO of anisole with an activation energy of 1.7 eV but more difficult than the HDO of phenol with an activation energy of 1.2 eV. The rate limiting steps in the HDO reactions are catechol dehydroxylation, anisole demethoxylation and phenol dehydroxylation. Our results show that ortho substituents impede C-O bond cleavage, as seen for catechol, whereas in the absence of an ortho substituent -OH cleavage is easier than -OCH3 cleavage to form benzene.

Evidence of defect-induced broadband light emission from 2D Ag-Bi double perovskites grown at liquid-liquid interfaces.

Controlling the light emission spectra of low-dimensional hybrid organic-inorganic materials remains an important goal toward the implementation of these materials into real-world optoelectronic devices. In this study, we present evidence that the self-assembly of two-dimensional (2D) silver bismuth iodide double perovskite derivatives at the interface of aqueous and organic solutions leads to the formation of defects capable of modulating the light emission spectra of these materials. Through an analysis of the structural parameters used to explain the photoluminescence (PL) spectra of 2D perovskites, we show the light spectra emitted by (4-ammonium methyl)piperidinium (4-AMP) and (3-ammonium methyl)pyridinium (3-AMPy)-spaced AgBiI8 double perovskites formed through interfacial solution-phase chemistry differ qualitatively and quantitatively from thin film samples. We use previous results to propose the differences observed in the PL spectra of different material morphologies stem from equatorial iodide vacancy formation driven by the kinetics of self-assembly at the liquid-liquid interface. These results show the generality of these chemical physics principles in the formation of defect sites in solution-processed semiconducting nanomaterials, which could help enable their broad use in optoelectronic technologies.