Highly Efficient Conversion of Propargylic Amines and CO2 Catalyzed by Noble-Metal-Free [Zn116] Nanocages

The reaction of propargylic amines and CO2 can provide high-value-added chemical products. However, most of catalysts in such reactions employ noble metals to obtain high yield, and it is important to seek eco-friendly noble-metalfree MOFs catalysts. Here, a giant and lantern-like [Zn-116] nanocage in zinc-tetrazole 3D framework [Zn-22(Trz)(8)(OH)(12)(H2O)(9.8) H2O](n) Trz = (C4N12O)(4-) (1) was obtained and structurally characterized. It consists of six [Zn14021 clusters and eight [Zn4O4] clusters. To our knowledge, this is the highestnuclearity nanocages constructed by Zn-clusters as building blocks to date. Importantly, catalytic investigations reveal that 1 can efficiently catalyze the cycloaddition of propargylic amines with CO2, exclusively affording various 2-oxazolidinones under mild conditions. It is the first eco-friendly noble metal-free MOFs catalyst for the cyclization of propargylic amines with CO2. DFT calculations uncover that Znii ions can efficiently activate both C C bonds ofpropargylic amines and CO, by coordination interaction. NMR and FTIR spectroscopy further prove that Zn-clusters play an important role in activating C C bonds ofpropargylic amines. Furthermore, the electronic properties of related reactants, intermediates and products can help to understand the basic reaction mechanism and crucial role of catalyst 1.