Construction\nof a Lanthanide Cage with a Hollow-Walled\nCavity and Large Windows to Promote Nucleophilic Additions

Metal–organic cages (MOCs) as artificial mimic\nenzymes can\nallow small organic molecules to freely move in and out of the cavity\nwith confined space, which often can increase intermolecular collisions\nand accelerate those reactions that are difficult to occur. This kind\nof homogeneous catalyst possesses high catalytic activity and regioselectivity,\nattracting growing interest recently. However, the rational design\nof MOCs with large openings as well as rich active sites for efficient\nchemical conversions remains a great challenge. Herein, we report\na decanuclear 3d-4f MOC, <b>Zn</b><sub><b>2</b></sub><b>Yb</b><sub><b>8</b></sub>, with a hollow-walled cavity and\nfour large windows self-assembled cooperatively by bridging ligands,\nZn-based metalloligands, and lanthanide Yb<sup>3+</sup> ions. The\nlantern-like <b>Zn</b><sub><b>2</b></sub><b>Yb</b><sub><b>8</b></sub> not only exposes unblocked passageways\nfor allowing more guest molecules to penetrate the cage smoothly but\nalso provides rich Lewis centers within the cavity, which could promote\nnucleophilic additions to effectively boost Friedel–Crafts\nalkylation and the three-component Strecker reaction. With the <b>Zn</b><sub><b>2</b></sub><b>Yb</b><sub><b>8</b></sub> catalyst, more than 13 bis(indolyl)methane derivatives could\nbe synthesized easily in 53–98% through Friedel–Crafts\nalkylation, and the conversion of the Strecker reaction for aniline,\nbenzaldehyde, and trimethylsilyl cyanide could achieve approximately\n98% in 3 h. Furthermore, host–guest relationship investigations\nconfirmed that the catalytic function of the <b>Zn</b><sub><b>2</b></sub><b>Yb</b><sub><b>8</b></sub> cage could\nbe mainly attributed to the synergy of the inherent confinement effect,\nmultiple Lewis catalytic sites, and host–guest electrostatic\ninteractions in the coordination cage. The construction of the discrete\n3d-4f MOC with large windows and its catalytic applications in nucleophilic\nadditions may represent a potential approach for developing enzyme-like\nsupramolecular nanoreactors.