Nanocage-based {SnEr₂}-organic framework for high catalytic performance in cycloaddition of CO₂ with epoxides and...

The integration of abundant active sites and robust chemical stability in metal-organic frameworks (MOFs) is pivotal for advancing their industrial-scale utilization. This study proposes a novel strategy to construct cluster-based heterometallic MOFs by incorporating rare-earth ions. Through a solvothermal synthesis approach, we successfully engineered {[SnEr₂(HBDCP)(H₂O)] _n ·3DFM·5H₂O} _n (TYUT-13), a three-dimensional framework integrating Sn²⁺ (stannous(ii) ions), Er³⁺ (erbium(iii) ions) and designed flexible tetracarboxylic acid of 2,6-bis(2,4-dicarboxylphenyl)-4-(4-carboxylphenyl)pyridine (H₅BDCP). This architecture features a unique pore environment characterized by high porosity and dual-functional active sites (Lewis acidic Sn/Er centers and basic pyridinic N atoms), which synergistically enhance catalytic performance. Experimental results demonstrate that TYUT-13a exhibits exceptional activity in the solvent-free cycloaddition of CO₂ to epoxides under mild conditions (65 °C, 1 atm CO₂, 4 h), achieving >98% conversion efficiency. Furthermore, it displays broad applicability in Knoevenagel condensations between phenoxyacetaldehyde and malononitrile, with yields exceeding 97%. These findings highlight the effectiveness of rare-earth ion hybridization in balancing structural integrity and catalytic multifunctionality, offering a blueprint for designing next-generation MOF catalysts for sustainable chemical processes.