Installation of Copper(I) and Silver(I) Sites into TREN-Based Porous Organic Cages via Postsynthetic Metalation

Porous organic cages (POCs) and metal–organic polyhedra (MOPs) function as zero-dimensional porous materials, able to mimic many functions of insoluble framework materials while offering processability advantages. A popular approach to access tailored metal-based motifs in extended network materials is postsynthetic metalation, which allows metal installation to be decoupled from framework assembly. Surprisingly, this approach has only sparingly been reported for molecular porous materials. In this report, we demonstrate postsynthetic metalation of tetrahedral [4 + 4] POCs assembled from tris(2-aminoethyl)amine (TREN) and 1,3,5-tris(4-formylphenyl)benzene. The trigonally symmetric TREN motif is a common chelator in coordination chemistry and, in the POCs explored herein, readily binds copper(I) and silver(I) to form cationic cages bearing discrete mononuclear coordination fragments. Metalation retains cage porosity, allowing us to compare the sorption properties of the parent organic and metalated cages. Interestingly, introduction of copper(I) facilitates activated oxygen chemisorption, demonstrating how targeted metalation can be exploited to tune the sorption characteristics of porous molecular materials.