PCN-222(Co) Metal–Organic Framework Nanorods Coated with 2D Metal–Organic Layers for the Catalytic Fixation of CO₂ to Cyclic Carbonates

In this work, a functionalized metal–organic layer (MTTB MOL) was first synthesized and characterized, where MTTB means that it was synthesized from TTB (4,4′,4″-s-triazine-2,4,6-triyl-tribenzoate). On this basis, a hybrid metal–organic framework of PCN-222­(Co)@MTTB was further synthesized by combining two-dimensional (2D) MTTB MOLs and three-dimensional (3D) PCN-222­(Co) MOFs (metal–organic frameworks) via a one-step method. When applied to the cycloaddition reaction of carbon dioxide (CO₂) and epoxides, PCN-222­(Co)@MTTB was found to exhibit excellent synergistic catalytic performance under mild conditions. The unique catalytic activity of the composite is due to the combination of the exposed acidic sites (Co²⁺, Zr⁴⁺) and basic sites (−N– groups) within the matrix of the MOF structure, thereby providing a new method for the exploration of effective catalysts for the conversion of CO₂ to value-added chemicals under mild conditions.