Rational Assembly of Multifunctional Fe/Mn MOF through Mixed-Linker and Defect Engineering for CO2 Cycloaddition...

The development of heterogeneous catalysts that cooperatively integrate multiple active sites within a defined architecture is critical for complex reactions such as the cycloaddition of CO2 to epoxides. Herein, a rational design strategy for constructing a defect-engineered bimetallic metal-organic framework (MOF) incorporating multiple catalytic functionalities is demonstrated. Through a mixed-metal (Fe/Mn) and mixed-linker (1,4-benzenedicarboxylic acid/4-aminobenzoic acid) synthesis strategy, a defective Fe/Mn MOF with layered nanosheet morphology was prepared via an ultrasonic-assisted method. This framework simultaneously incorporates: (i) Lewis basic amine functionalities for CO2 interaction and activation, (ii) defect-induced coordinatively unsaturated metal sites serving as Lewis acidic centers for epoxide activation, and (iii) bimetallic nodes that provide a modulated catalytic environment within the framework. Comprehensive characterization including XRD, XPS, 1H NMR, BET, TGA, ICP-OES, and SEM confirms the successful construction of the designed framework and reveals an enhanced surface area compared with its non-defective analogue. Under optimized solvent-free conditions, the catalyst achieved a styrene oxide conversion of 87%, substantially outperforming non-defective and monometallic control MOFs. This work demonstrates a targeted strategy for multifunctional MOF catalysts in which the synergistic integration of mixed-metal chemistry, linker functionalization, defect engineering, and morphology control enhances catalytic performance for sustainable CO2 conversion.