Room-temperature selective cyclodehydrogenation on Au(111) via radical addition of open-shell resonance structures.

Cyclodehydrogenation is an important ring-formation reaction that can directly produce planar-conjugated carbon-based nanomaterials from nonplanar molecules. However, inherently high C-H bond energy necessitates a high temperature during dehydrogenation, and the ubiquity of C - H bonds in molecules and small differences in their bond energies hinder the selectivity of dehydrogenation. Here, we report a room-temperature cyclodehydrogenation reaction on Au(111) via radical addition of open-shell resonance structures and demonstrate that radical addition significantly decreases cyclodehydrogenation temperature and further improves the chemoselectivity of dehydrogenation.

Two-Dimensional Crystal Transition from Radialene to Cumulene on Ag(111) via Retro-[2 + 1] Cycloaddition.

Two-dimensional (2D) crystal-to-crystal transition is an important method in crystal engineering because of its ability to directly create diverse crystal materials from one crystal. However, steering a 2D single-layer crystal-to-crystal transition on surfaces with high chemo- and stereoselectivity under ultra-high vacuum conditions is a great challenge because the transition is a complex dynamic process. Here, we report a highly chemoselective 2D crystal transition from radialene to cumulene with retention of stereoselectivity on Ag(111) via retro-[2 + 1] cycloaddition of three-membered carbon rings and directly visualize the transition process involving a stepwise epitaxial growth mechanism by the combination of scanning tunneling microscopy and non-contact atomic force microscopy.

On-Surface Cross-Coupling Reactions.

On-surface synthesis, as a bottom-up synthetic method, has been proven to be a powerful tool for atomically precise fabrication of low-dimensional carbon nanomaterials over the past 15 years. This method relies on covalent coupling reactions that occur on solid substrates such as metal or metal oxide surfaces under ultra-high-vacuum conditions, and the achievements with this method have greatly enriched fundamental science and technology. However, due to the complicated reactivity of organic groups, distinct diffusion of reactants and intermediates, and irreversibility of covalent bonds, achieving the high selectivity of covalent coupling reactions on surfaces remains a great challenge.

[Analysis of Spatiotemporal Variation Characteristics and Driving Forces of NPP in Shanxi Province from 2000 to 2020 Based on Geodetector].

The net primary productivity (NPP) of vegetation, as an indispensable element in carbon cycle studies, characterizes plant growth status. This study applied MODIS NPP products from 2000 to 2020 and multi-source data on elevation, slope, precipitation, temperature, land use, and population density in Shanxi province. We used trend analysis, correlation analysis, and geographic probes to explore the spatial and temporal evolution characteristics and driving factors of NPP in Shanxi province and its national planned coal-mining areas.