Hierarchical Acid–Base–Hydrogen-Bond Synergy in a Defect-Tolerant 2D Lanthanide MOF for Efficient CO ₂ –Epoxide Cycloaddition

The catalytic conversion of carbon dioxide into value-added chemicals remains a central challenge in sustainable catalysis. Herein, we report a defect-tolerant two-dimensional ytterbium–organic framework, NUC-205, constructed through dimensionality reduction and ligand functionalization. Upon activation, NUC-205a features accessible Lewis-acidic Yb 3+ centers, Lewis-basic amino and pyridyl groups, and hydrogen-bond-donating carboxyl moieties within the porous framework. These complementary sites generate an integrated acid–base–hydrogen-bond microenvironment, enabling highly efficient CO 2 –epoxide cycloaddition, affording near-quantitative yields even under simulated dry and humid flue-gas atmospheres. Density functional theory (DFT) calculations show that NH 2 sites exhibit the lowest rate-determining step activation barriers, revealing a clear activity hierarchy among different active sites. Notably, the defect-tolerant 2D architecture preserves high activity and recyclability under partial hydration of the metal centers. This work provides mechanistic insight into the cooperative catalysis, highlighting the contribution of organic functional sites, and offers a general design principle for moisture-resilient MOF catalysts.