Nanocage-Based In^III{Tb^III}₂-Organic Framework Featuring Lotus-Shaped Channels for Highly Efficient CO₂ Fixation and I₂ Capture

The exquisite combination of independent 3p [In(CO2)4] units and 4f [Tb2(CO2)8] clusters in the presence of the designed hexatopic 2,4,6-tri(2,4-dicarboxyphenyl)pyridine ligand engenders one peculiar nanocaged In(III){Tb(III)}2-organic framework: ({(Me2NH2)[InTb2(HTDP)2]·3DMF·3H2O}n, designated as NUC-5), which features dual types of lotus-shaped channels along the [100] and [110] axes with related node windows of 5.3 × 6.8 and 12.1 × 9.2 Å2, respectively. To the best of our knowledge, except several coexisted 3p-4f In/Ln clusters of {In3Ln}- and {In3Ln2}-based metal–organic frameworks (MOFs), NUC-5 is one novel type of In/Ln heterometallic framework. In addition, its topology was an unprecedented 3D TAYZIC net with a Schläfli symbol of {4.462}{4.565}2{4.66.88}. Moreover, activated NUC-5 is proved to be one efficient adsorbent for CO2 and one recycled cycloaddition catalyst for the transformation of epoxides into related carbonates with high yields under mild conditions. Furthermore, the excellent reversible sorption performance for I2 in the volatilization phase or in cyclohexane solution with a maximum adsorption capacity of 609.1 mg/g (3.75 iodine molecules per unit cell) makes NUC-5 a promising adsorbent for radioactive products of 129I and 131I in the field of nuclear industry. This study provides one synthetic strategy that the original nature of MOFs could be enhanced by introducing some specific function-prompted inorganic subunits with the aid of predesigned supporting ligands.