Combinatorial Self-Assembly of Coordination Cages with Systematically Fine-Tuned Cavities for Efficient Co-Encapsulation and Catalysis

Controllable arrangement of different ligands in a single assembly will not only bring increased complexity but also offers a new route to fine-tune the function of the designed architecture. We report here a combinatorial self-assembly with enPd(NO3)(2) and three different ligands (L1-3), which gave rise to a family of six palladium-organic cages (C1-6) with systematically varied shapes and cavities, including three new heteroleptic ((Pd5L2L2)-L-1, (Pd5L2L3)-L-1, (Pd4LL3)-L-2), one new homoleptic (Pd4L23) cages, and two known homoleptic (Pd6L41, Pd4L22) cages. Emergent functions due to the fusion of two half cavities on the heteroleptic cages from their parent homoleptic cages have been observed: the heteroleptic cages can form ternary complexes by co-encapsulation of both aromatic and aliphatic guests, while their homoleptic counterparts can only form binary complexes. Such a forced co-encapsulation effect endows the heteroleptic cages with enhanced catalytic power for the Knoevenagel condensation.

Automated summary

This study demonstrates a combinatorial self-assembly method to synthesize a family of palladium-organic cages with systematically varied shapes and cavities by using different ligand combinations. The formation of heteroleptic cages leads to the emergence of new functions, enabling the co-encapsulation of both aromatic and aliphatic guests and enhancing the catalytic power in the Knoevenagel condensation.