Defect-engineered indium-organic framework displays the higher CO 2 adsorption and more excellent catalytic performance on the cycloaddition of CO 2 with epoxides under mild conditions.

In order to achieve the high adsorption and catalytic performance of CO 2 , the direct self-assembly of robust defect-engineered MOFs is a scarcely reported and challenging proposition. Herein, a highly robust nanoporous indium(III)-organic framework of {[In 2 (CPPDA)(H 2 O) 3 ](NO 3 )·2DMF·3H 2 O} n (NUC-107) consisting of two kinds of inorganic units of chain-shaped [In(COO) 2 (H 2 O)] n and watery binuclear [In 2 (COO) 4 (H 2 O) 8 ] was generated by regulating the growth environment. It is worth mentioning that [In 2 (COO) 4 (H 2 O) 8 ] is very rare in terms of its richer associated water molecules, implying that defect-enriched metal ions in the activated host framework can serve as strong Lewis acid. Compared to reported skeleton of [In 4 (CPPDA) 2 (μ 3 -OH) 2 (DMF)(H 2 O) 2 ] n (NUC-66) with tetranuclear clusters of [In 4 (μ 3 -OH) 2 (COO) 10 (DMF)(H 2 O) 2 ] as nodes, the void volume of NUC-107 (50.7%) is slightly lower than the one of NUC-66 (52.8%). However, each In 3+ ion in NUC-107 has an average of 1.5 coordinated small molecules (H 2 O), which far exceeds the average of 0.75 in NUC-66 (H 2 O and DMF). After thermal activation, NUC-107a characterizes the merits of unsaturated In 3+ sites, free pyridine moieties, solvent-free nanochannels (10.2 × 15.7 Å 2 ). Adsorption tests prove that the host framework of NUC-107a has a higher CO 2 adsorption (113.2 cm 3 /g at 273 K and 64.8 cm 3 /g at 298 K) than NUC-66 (91.2 cm 3 /g at 273 K and 53.0 cm 3 /g at 298 K). Catalytic experiments confirmed that activated NUC-107a with the aid of n-Bu 4 NBr was capable of efficiently catalyzing the cycloaddition of CO 2 with epoxides into corresponding cyclic carbonates under the mild conditions. Under the similar conditions of 0.10 mol% MOFs, 0.5 mol% n-Bu 4 NBr, 0.5 MP CO 2 , 60 °C and 3 h, compared with NUC-66a, the conversion of SO to SC catalyzed by NUC-107a increased by 21%. Hence, this work offers a valuable perspective that the in situ creation of robust defect-engineered MOFs can be realized by regulating the growth environment.