Supported Molybdenum Oxides for the Aldol Condensation Reaction of Acetaldehyde

Simultaneous High-Efficiency Photocatalytic Production of H2O2 and Synthesis of 3-HBA Using COFs Broadened by π Conjugate Networks and Photogenerated Charges

The coupling of H2O2 photosynthesis with photogenerated electrons and holes, when used separately, not only realizes the production of value-added products but also maximizes energy utilization. However, achieving this remains a challenge. Here, we report three variations of triazine-based covalent organic frameworks (COFs) featuring phenyl π-π-conjugated structures and furthermore introduce the phenoxy COF with a p-π-conjugated structure as a control to effectively produce hydrogen peroxide. It is found that the strong π-π conjugate network triggers a pronounced optical response and provides channels for charge transfer and electron enrichment. The results showed that the H2O2 yield of TTBA-TP-COF (TTBA = 4,4,4-(1,3,5-triazine-2,4,6-triyl) tris (([1,1-biphenyl]-4-amine)), TP = 2,4,6-triformylphloroglucinol) reached an impressive 11,982 μmol/g/h, which was 1.49 times, 8.77 times, and 7.20 times that of TAPT-TP-COF (TAPT = 4,4',4″-(1,3,5-triazine-2,4,6-triyl)trianiline), MA-TP-COF (MA = melamine), and TTTT-TP-COF (TTTT = 4,4',4″-((1,3,5-triazine-2,4,6-triyl)tris(oxy))trianiline), respectively. Considering the atomic economy, we pioneeringly put forward the strategy of using photogenerated electrons and holes separately. Concurrently, with the photocatalytic production of hydrogen peroxide, acetaldehyde produced by hole oxidation, sacrificial ethanol served as primary feedstock, and aldol condensation of acetaldehyde was successfully catalyzed to produce 3-hydroxybutyraldehyde (3-HBA) under alkaline conditions provided by a small amount of triethylamine. The concentration of 3-HBA produced was confirmed to be 23.84 mmol/L by means of mass spectrometry and high-performance liquid chromatography.

Gas-phase organometallic catalysis in MFM-300(Sc) provided by switchable dynamic metal sites

MFM-300(Sc) was explored as a catalyst for the gas-phase hydrogenation of acetone. The catalysis results support the presence of non-permanent open Sc(III) sites within the structure due to the requirement of Lewis acid sites for the reaction to proceed. The open Sc(III) sites are generated in situ due to the presence of hemilabile Sc-O bonds. MFM-300(Sc) showed high mechanical and chemical stability, and the crystalline structure was maintained after the catalytic reaction. The catalytic activity of the material was quantified by performing a gas-phase reaction using a continuous flow reactor. The acetone conversion in MFM-300(Sc) was estimated to be 27.7% with no loss of activity after catalytic cycles.