6s-3d {BaZn}-Organic Framework as an Effective Heterogeneous Catalyst for Chemical Fixation of CO and Knoevenagel Condensation Reaction.

The exquisite combination of Ba and Zn with the aid of 2,4,6-tri(2,4-dicarboxyphenyl)pyridine (HTDP) under the condition of solvothermal self-assembly generates one highly robust [BaZn(CO)(HCO)(OH)]-organic framework of {[BaZn(TDP)(HCO)(OH)]·7DMF·4HO} (), in which adjacent 2D layers are interlaced via hydrogen-bonding interactions to form a 3D skeleton with peapod-like channels and nano-caged voids. It is worth emphasizing that both Ba and Zn ions in display the extremely low coordination modes: hexa-coordinated [Ba(1)] and tetra-coordinated [Ba(2), Zn(1), and Zn(2)]. Furthermore, to the best our knowledge, is one scarcely reported 2D-based nanomaterial with an unprecedented Z-shaped hepta-nuclear heterometallic cluster of [BaZn(CO)(HCO)(OH)] as SBUs, which not only has plentiful low-coordinated open metal sites but also has the excellent physicochemical properties including omni-directional opening pores, ultrahigh porosity, larger specific surface area, and the coexistence of Lewis acid-base sites. Just as expected, thanks to its rich active metal sites and pyridine groups as strong Lewis acid-base roles, completely activated displays high catalytic efficiency on the chemical transformation of epoxides with CO into cyclic carbonates under mild conditions and effectively accelerates the reaction process of Knoevenagel condensation.