Highly Selective Enamination of β-ketoesters Catalyzed by Interlocked [Cu₈ ] and [Cu₁₈ ] Nanocages

Interlocking cages are of great interest due to their fascinating structures and potential applications. However, the interlocking of different cages has not been previously reported. Herein, quadruply interlocked [Cu₈ ] and [Cu₁₈ ] nanocages have been constructed and structurally characterized in cationic metal-organic framework {[Cu^I Cu₄ ^II (XN)₄ (PTA)₄ (H₂ O)₄ ]0.5 SO₄ ⋅5 H₂ O⋅EtOH}_n (1). 1 can trap the anionic pollutant CrO₄ ^2- and the radioactive-contaminant simulant ReO₄ ^- with an uptake capacity of 83.2 and 218 mg g^-1 , respectively. Catalytic investigations reveal 1 is an efficient heterogeneous catalyst for the enamination of ethyl acetoacetate with aniline and the turnover frequency (TOF) can reach a record value of 4000 h^-1 . More importantly, 1 represents the first of a catalyst of enamination to exhibit excellent size selectivity on different substrates. The robust catalyst can be reused at least ten times without obvious loss in catalytic activity.