Unlocking High Porosity: Post‐Synthetic Solvothermal Treatment of Cu‐Paddlewheel Based Metal–Organic Cages

Abstract

AbstractMetal–organic cages (MOCs) have garnered significant attention due to their unique discrete structures, intrinsic porosity, designability, and tailorability. However, weak inter‐cage interactions, such as van der Waals forces and hydrogen bonding can cause solid‐state MOCs to lose structural integrity during desolvation, leading to the loss of porosity. In this work, a novel strategy to retain the permanent porosity of Cu‐paddlewheel‐based MOCs, enabling their use as heterogeneous catalysts is presented. Post‐synthetic solvothermal treatments in non‐coordinating solvents, mesitylene, and p‐xylene, effectively preserve the packing structures of solvent‐evacuated MOCs while preventing cage agglomeration. The resulting MOCs exhibit an exceptional N2 sorption capacity, with a high surface area (SBET = 1934 m2 g−1 for MOP‐23), which is among the highest reported for porous MOCs. Intriguingly, while the solvothermal treatment reduced Cu(II) to Cu(I) in the Cu‐paddlewheel clusters, the MOCs with mixed‐valenced Cu(I)/Cu(II) maintained their crystallinity and permanent porosity. The catalytic activities of these MOCs are successfully examined in copper(I)‐catalyzed hydrative amide synthesis, highlighting the prospect of MOCs as versatile reaction platforms.