Structure-Directed Two-Dimensional {Eu₂} Metal-Organic Framework with Cooperative Acid-Base Microenvironments for...

Two-dimensional metal-organic frameworks (2D MOFs) hold exceptional promise as heterogeneous catalysts owing to their expanded external surfaces and maximized accessibility of active sites, yet the deliberate construction of chemically robust systems with cooperative catalytic microenvironments remains elusive. Herein, we present a structure-directed strategy for assembling a stable 2D {Eu₂}-MOF, {[Eu(HTPPDDC)(DMF)₂(H₂O)₂]·2DMF·2H₂O} (NUC-195), derived from Eu(III) centers and a trifluoromethyl-decorated pyridyl dicarboxylate linker. Thermal activation yields NUC-195a, featuring well-defined in-plane nanopores and a hierarchically integrated catalytic landscape composed of Lewis-acidic Eu³⁺ sites, Brønsted-acidic carboxyl groups, and Lewis-basic pyridyl moieties. The precise spatial convergence of these functionalities engenders a cooperative acid-base microenvironment within confined channels. As a consequence, NUC-195a catalyzes solvent-free CO₂/epoxide cycloaddition using 0.10 mol % catalyst and 1.0 mol % n-Bu₄NBr at 100 °C and 1.0 MPa CO₂ and also promotes tandem deacetalization-Knoevenagel condensation using 0.50 mol % catalyst at 60 °C. Mechanistic investigations supported by density functional theory calculations elucidate that synergistic substrate activation by adjacent acid and base sites substantially lowers reaction barriers. This work establishes a versatile 2D {Eu₂}-MOF catalyst and offers a generalizable paradigm for engineering cooperative microenvironments in functional MOFs.