RESUMEN
3D porous organic frameworks, which possess the advantages of high surface area and abundant exposed active sites, are considered ideal platforms to accommodate single atoms (SAs) and metal nanoclusters (NCs) in high-performance catalysts; however, very little research has been conducted in this field. In the present work, a 3D porous organic framework containing Ni1 SAs and Nin NCs is prepared through the metal-assisted one-pot polycondensation of tetraaldehyde and hexaaminotriptycene. The single metal sites and metal clusters confined in the 3D space created a favorable micro-environment that facilitated the activation of chemically inert CO2 molecules, thus promoting the overall photoconversion efficiency and selectivity of CO2 reduction. The 3D-NiSAs/NiNCs-POPs, as a CO2 photoreduction catalyst, demonstrated an exceptional CO production rate of 6.24 mmol g-1 h-1, high selectivity of 98%, and excellent stability. The theoretical calculations uncovered that asymmetrical interaction between Ni1 SAs and Nin NCs not only favored the bending of CO2 molecules and reducing the CO2 reduction energy, but also regulated the electronic structure of the catalyst leading to the optimal binding strength of intermediates.
RESUMEN
The development of facile tailoring approach to adjust the intrinsic activity and stability of atomically-precise metal nanoclusters catalysts is of great interest but remians challenging. Herein, the well-defined Au8 nanoclusters modified by single-atom sites are rationally synthesized via a co-eletropolymerization strategy, in which uniformly dispersed metal nanocluster and single-atom co-entrenched on the poly-carbazole matrix. Systematic characterization and theoretical modeling reveal that functionalizing single-atoms enable altering the electronic structures of Au8 clusters, which amplifies their electrocatalytic reduction of CO2 to CO activity by ~18.07 fold compared to isolated Au8 metal clusters. The rearrangements of the electronic structure not only strengthen the adsorption of the key intermediates *COOH, but also establish a favorable reaction pathway for the CO2 reduction reaction. Moreover, this strategy fixing nanoclusters and single-atoms on cross-linked polymer networks efficiently deduce the performance deactivation caused by agglomeration during the catalytic process. This work contribute to explore the intrinsic activity and stability improvement of metal clusters.
RESUMEN
Metabolic networks can provide insight into the biosynthesis pathways of natural products present in plant-derived medicines. Here, we primarily established a highly efficient and targeted method for the systematic screening of isoquinoline alkaloids from the Macleaya genus. A total of 392 potential alkaloids were detected, 204 of which were further identified according to their tandem mass spectrometry (MS/MS) spectra and the characteristic fragmentation patterns of references. A metabolic network of isoquinoline alkaloids from the Macleaya genus was then constructed based on the structural relationships, metabolic level differences, and the isotopically labeled [ring-13C6]-tyrosine feeding experiments. New biosynthesis pathways for well-known alkaloids (berberine, sanguinarine, and chelerythrine) in the Macleaya genus were proposed on the basis of the established metabolic network. This work marks the first comprehensive study of the metabolic network of isoquinoline alkaloids in the Macleaya genus and provides a template for constructing the metabolic networks of other plant-derived medicines.