Molecular Junction Polyoxotungstate-based Copper-Organic Frameworks for Photocatalytic Cross-Dehydrogenative Coupling.

The cross-dehydrogenative coupling (CDC) of tertiary amines and terminal alkynes is a vital catalysis step in the manufacture of C─C bonds. The traditional thermal catalysis, utilizing noble metal salts or toxic solvents, generally results in relatively low atom economy or unmet sustainable development prospect. The challenge of the CDC reactions lies in the simultaneous activation of C─H bonds in terminal alkynes and formation of free radical activation of tertiary amines to achieve the C─C coupling, which calls for novel catalytic techniques and powerful catalysts. For the first time, in exclusively green solvent (i.e., dimethyl carbonate), full light, and air, we have developed a series of molecular junction polyoxotungstate-based copper-organic frameworks (i.e., Cu-POMOF-1, Cu-POMOF-2, and Cu-POMOF-3), each with unique topological dimension and well-regulated charge transfer ability that can be utilized in efficient photocatalytic CDC reactions. Notably, the optimal Cu-POMOF-3 with the combination of polyoxotungstate and Cu sites within the 3D POMOF topological structure enables the simultaneous activation and C─C coupling of tertiary amines and terminal alkynes with 98% yield. In addition, the reaction system enables scale-up production (2.06 g in a batch experiment) and operation under natural sunlight and air.