Heterometallic YbCo–Organic Framework for Efficiently Catalyzing Cycloaddition of CO<sub>2</sub> with Epoxides and Knoevenagel Condensation
Hongxiao Lv, Liming Fan, Chenxu Jiao, Xiutang Zhang
Abstract
Due to the excellent catalytic performance of Co-MOFs and Ln-MOFs on the chemical fixation of CO 2, the self-assembly of microporous heterometallic compounds with the aid of designed functional ligands is carried out in our group. Herein, the solvothermal self-assembly of Co 2+, Yb 3+, and 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H 5 BDCP) generated a rarely reported {CoYb} n -chain-based framework of {[CoYb(BDCP)(H 2 O)]·3DMF·3H 2 O} n ( NUC-70 ) with quasi-nanoporous channels (aperture ca . 11.4 Å) shaped by six rows of {CoYb(CO 2 ) 5 (H 2 O)} n nodes. To the best of our knowledge, this is a rare 3d-4f heterometallic chain of {CoYb(CO 2 ) 5 (H 2 O)} n with a staggered arrangement of Co 2+ and Yb 3+ . After removing the associated water molecules, NUC-70a possesses the excellent characteristics of a large specific surface area, unsaturated open metal sites of Co 2+ and Yb 3+ as Lewis acid sites, and high heat/water-resistant physicochemical properties. Catalytic experiments showed that NUC-70a possessed a high catalytic activity on the cycloaddition reactions of epoxides with CO 2 under mild conditions. Furthermore, the experiments performed confirmed that the Knoevenagel condensation reactions of aldehydes and malononitrile could be efficiently catalyzed by NUC-70a . This work illustrates that characteristic ligand design plays a key role in the self-assembly of MOFs with specific functions.