Green carbon science: fundamental aspects

Substrate-Controlled Divergent Reductive Cyclization of 2-Arylanilines Using CO2 as a Switching Reagent

Capturing CO2 is highly valued in the field of organic synthesis, especially underdeveloped dual-CO2 conversion. In this study, we detail a novel reductive cyclization of 2-indolylanilines with dual CO2 as a difunctional reagent in the presence of PMHS [poly(methylhydrosiloxane)], delivering methyl-substituted quinoxalines. Furthermore, another chemoselective cyclization with 2-pyrrolylanilines is also realized by converting mono-CO2. Mechanistic investigations shed light upon the fact that this substrate-controlled divergence mainly depends on the formation of N-diacylative intermediates.

Samarium-Oxo/Hydroxy Cluster: A Solar Photocatalyst for Chemoselective Aerobic Oxidation of Thiols for Disulfide Synthesis

Oxidation contributes as a secondary driver of the prevailing carbon emission in the chemical industries. To address this issue, photocatalytic aerobic oxidation has emerged as a promising alternative. However, the challenge of achieving satisfactory chemoselectivity and effective use of solar light has hindered progress in this area. In this context, the present study introduces a novel homogeneous photocatalyst, [Sm6O(OH)8(H2O)24]I8(H2O)8 cluster (Sm-OC), via a unique auxiliary ligand-free oxidative hydrolysis. Using Sm-OC as catalyst, a solar photocatalyzed aerobic oxidation of thiols has been developed for the synthesis of valuable disulfides. Remarkably, this catalyst manifested a significant turnover number ≥2000 under tested conditions. Sm-OC-catalyzed aerobic oxidation showcased remarkable chemoselectivity. In thiol oxidations, despite the vulnerability of disulfides toward overoxidation, overoxidized byproducts or oxidation of nontarget functional groups was not detected across all 28 tested substrates. This investigation presents the first application of a lanthanide-oxo/hydroxy cluster in photocatalysis.

Tandem catalysts of different crystalline In2O3/sheet HZSM-5 zeolite for CO2 hydrogenation to aromatics

In tandem catalysts, not only good synergy between the two active components is required, but also the precise control of the spatial distribution between the two active components of metal oxides and zeolite is crucial for the migration and conversion of reaction intermediates in the direct conversion of CO2 to hydrocarbons. The correlation between the metal and the acidic site of zeolite has traditionally been simplified as "the closer, the better". However, it should be noted that this principle only holds true for a portion of tandem catalysts. Therefore, this paper studied the effect of different crystalline In2O3 (cubic phase, hexagonal phase, and mixed cubic/hexagonal phase) and sheet HZSM-5 zeolite tandem catalysts on the activity of CO2 hydrogenation reaction under different spatial distribution. The generalized gradient approximation (GGA) of density functional theory (DFT) were used to simulate the adsorption energy of CO2 by oxygen vacancy on c-In2O3(111) and h-In2O3(104) planes, it was found that Ov1 on c-In2O3(111) and Ov4 on h-In2O3(104) had the strongest adsorption energy for CO2. In addition, it has been observed that the proximity of the two active components (e.g., during mortar mixing) results in decreased catalytic performance. This is due to the migration of metal In, which neutralizes the acid sites of zeolites and leads to inefficient conversion of methanol reaction intermediates to aromatics. As a result, CO2 conversion and aromatic selectivity are decreased.

P-Band Intermediate States Mediate Electron Transfer at Confined Nanoscale

In this Perspective, mainly based on the model of structural water molecules (SWs) as bright color emitters, we briefly summarize the development and theoretical elaboration of P-band intermediate state (PBIS) theory as well as its application in several typical catalytic redox reactions. In addition, with a simple equation (2∫ψ2σ1' + ∫ψ2σ2 + ∫ψ2π = 1), we clearly define how the interface states correlate with the three basic parameters of heterogeneous catalysis (conversion, selectivity, and stability), and what is the dynamic nature of catalytic active sites. Overall, the proposal of SW-dominated PBIS theory establishes an internal physical connection between the decay kinetics of excited electrons and the catalytic reaction kinetics and provides new insights into the physical origin of photoluminescence emission of low-dimensional quantum nanodots and the physical nature of nanoconfinement and nanoconfined catalysis.

Science-an important lever to tackle sustainability in the specialty chemical industry

Achieving carbon neutrality in the chemical industry necessitates a green and efficient transformation. Working together, industry and academia hold the key to developing clean chemical processes, which is crucial.

Defective PrOx for Efficient Electrochemical NO2−-to-NH3 in a Wide Potential Range

Electrocatalytic reduction of nitrite (NO2−) is a sustainable and carbon-neutral approach to producing green ammonia (NH3). We herein report the first work on building defects on PrOx for electrochemical NO2− reduction to NH3, and demonstrate a high NH3 yield of 2870 μg h−1 cm−2 at the optimal potential of –0.7 V with a faradaic efficiency (FE) of 97.6% and excellent FEs of >94% at a wide given potential range (−0.5 to −0.8 V). The kinetic isotope effect (KIE) study suggested that the reaction involved promoted hydrogenation. Theoretical calculations clarified that there was an accelerated rate-determining step of NO2− reduction on PrOx. The results also indicated that PrOx could be durable for long-term electrosynthesis and cycling tests.