Bromine-Functionalized Lanthanide MOF with Acid–Base Dual Active Sites: Catalysis for CO2 Cycloaddition and N-Formylation

Metal–organic frameworks (MOFs) represent a prominent research direction for the heterogeneous catalytic conversion of carbon dioxide (CO2), with substantial implications for resource utilization and sustainable development. Herein, a bromine-functionalized lanthanide MOF (Eu-DBT) was synthesized via solvothermal reaction of Eu3+ ions with 2,5-dibromoterephthalic acid (H2DBT), constructing a bifunctional acid–base catalytic system. Eu-DBT exhibits excellent catalytic performance in two key CO2 fixation reactions. It achieves a 98.4% yield and 99.5% selectivity for the cycloaddition of CO2 with propylene oxide, and 99.8% conversion with a 99.4% target yield for N-methylaniline CO2 mediated N-formylation under optimized conditions. Additionally, Eu-DBT demonstrates broad substrate generality and robust recyclability, retaining high activity over five consecutive reaction cycles. Mechanistic investigations reveal that its superior performance originates from the synergistic effect of Eu3+ and −Br acid–base dual active sites, which effectively reduce reaction energy barriers. This work provides a ligand halogenation strategy for rational designing multifunctional Ln-MOFs, highlighting bromine-functionalized Ln-MOFs as efficient heterogeneous catalysts for sustainable CO2 resource utilization.