ABSTRACT
A series of pyridine-type ligands containing C≡C bonds were designed and synthesized for selective oxidative Heck reaction. These ligands were utilized as functional units and integrated into the skeleton of conjugated microporous polymers. 6,6'-diiodo-2,2'-bipyridine and 1,3,5-triethynylbenzene were polycondensed via Sonogashira cross-coupling strategy to afford CMP-1 material. The resultant CMP-1 was used as a heterogeneous catalytic ligand for the PdII-catalyzed oxidative Heck reaction with high linear selectivity. The linear selectivity of CMP-1 is about 30 times higher than that of bipyridine-based monomer ligand. This work opens a new front of using CMP as an intriguing platform for developing highly efficient catalysts in controlling the regioselectivity in organic reactions.
ABSTRACT
Crystal facet engineering of semiconductors has been proven to be an effective strategy to increase photocatalytic performances. However, the mechanism involved in the photocatalysis is not yet known. Herein, we report our success in that photocatalytic performances of the Cl(-) ion capped CoO octahedrons with exposed {111} facets were activated by a treatment using AgNO3 and NH3·H2O solutions. The clean CoO {111} facets were found to be highly reactivity faces. On the basis of the polar structure of the exposed {111} surfaces, a charge separation model between polar {111} surfaces is proposed. There is an internal electric field between polar {111} surfaces due to the spontaneous polarization. The internal electric field provides a driving force for charge separation. The reduction and oxidation reactions selectively take place on the positive and negative polar {111} surfaces. The charge separation model provides a clear insight into charge transfer in the semiconductor nanocrystals with high photocatalytic activities and offer guidance to design more effective photocatalysts, solar cells, photoelectrodes, and other photoelectronic devices.