Dual-linker metal-organic frameworks as efficient carbon dioxide conversion catalysts

In the present work, two dual-linker metal-organic frameworks (MOFs) were prepared with metal salts, terephthalic acid and 4, 4'-bipyridine as precursors, and subsequently used for preparing cyclic carbonates from carbon dioxide and epoxides. These two MOFs were characterized by a number of techniques. The two MOFs prepared showed superior catalytic performance under solventless and co-catalyst-free conditions. In this sense, Co(tp)(bpy) achieved epichlorohydrin (ECH) conversions as high as 95.75% and chloropropylene carbonate (CPC) yields of 94.18% under optimal reaction conditions. The high activity of Co(tp)(bpy) was attributed to the co-existence of Lewis acidic and basic active sites on the catalyst derived from incompletely coordinated metal cations and uncoordinated pyridine groups, respectively. In addition, Co(tp)(bpy) maintained this high catalytic performance after five consecutive reaction cycles. A possible reaction mechanism was proposed based on the experimental results.