Two Ln-MOFs containing abundant Lewis acid sites as the efficient and heterogeneous catalyst to activate epoxides for cycloaddition of CO2.

• MOFs 1–2 show a 3D supramolecular network structure with microporous. • MOFs 1–2 have abundant active sites of Lewis acid due to the fact that the metal center of MOFs 1–2 is rare earth metal. • MOFs 1–2 have good catalytic activity for the chemical fixation of carbon dioxide with epoxides under mild conditions. • MOFs 1–2 showed universality and remarkable conversion for epoxides of different sizes. The burning of a large number of fossil fuels leads to the increase of CO 2 content in the air, causing environmental problems such as greenhouse effect and ocean acidification, which has attracted wide attention. It is of great significance to utilize microporous metal-organic frameworks (MOFs) for carbon dioxide conversion and utilization. Herein, two MOFs {[Ln(dppa)(H 2 O) 2 ·2H 2 O]·dima·H 2 O·0.5O} (1: Sm-MOF; 2: Gd-MOF; H 4 dppa = 5-(3′ 4′-dicar- boxylphenoxy) isophthalic acid, dima = dimethylamine, which is decomposed by DMF hydrothermal reaction), and its structural characterization and CO 2 catalytic conversion performance were studied. The BET test of MOFs 1–2 shows that it has good microporosity. At 273 K and 298 K, MOFs 1–2 showed lower adsorption capacity for CH 4 , but higher adsorption capacity for CO 2. The adsorption enthalpy of CO 2 was calculated by Virial equation, and the adsorption selectivity of CO 2 at different separation ratios was discussed respectively. The heterogeneity of MOFs 1–2 was proved by thermal filtration experiments. The reproducibility test shows that the catalyst structure is still intact after five cycles, indicating that the catalyst still has good repeatability. In addition, the catalytic mechanism of cycloaddition reaction was discussed. The low coordination Ln-MOFs not only exhibit abundant Lewis acidsites, but also show high catalytic activity and selectivity in the CO 2 cycloaddition reaction, as well as strong recyclability and substrate versatility. In addition, the catalytic mechanism of cycloaddition reaction was discussed. [Display omitted] [ABSTRACT FROM AUTHOR]