Metal cluster-modified Zr-MOF: A versatile catalyst for cycloaddition and N-formylation reactions

The catalytic conversion of carbon dioxide into value-added chemicals under mild conditions represents a promising strategy for sustainable synthesis. In this study, we report the design and application of Fe-Ni cluster-modified UiO-66 (UFN) as a bifunctional metal–organic framework (MOF) catalyst for two green transformations: the cycloaddition of styrene oxide and CO₂ to yield styrene carbonate, and the N-formylation of aniline with formic acid to afford formanilide. The UiO-66 framework was successfully functionalized with bimetallic Fe–Ni clusters via a facile sol–gel approach, preserving its crystallinity while introducing catalytically active metal centers. Structural analyses confirmed that the Fe–Ni incorporation did not disrupt the framework integrity but created accessible Lewis acid sites. Notably, CO₂ adsorption measurements demonstrated significantly enhanced uptake capacities for the functionalized materials, reaching up to 3.22 mmol g⁻¹ at 273 K. The highest isosteric heat of adsorption (Qst = 42.52 kJ mol⁻¹) observed for UFN-40 indicates strong CO₂ framework interactions, attributed to the synergistic effect of Fe and Ni clusters within the porous structure. The UFN-40 material also demonstrated excellent catalytic activity, achieving 96.5 % conversion and 100 % selectivity in the cycloaddition reaction under 1 atm CO₂ at 100 °C, and retained high stability and recyclability over multiple cycles. Furthermore, UFN-40 efficiently catalyzed the N-formylation of aniline under ambient conditions, reaching 99 % conversion within 5 h. These findings highlight the potential of Fe–Ni cluster-modified Zr-MOFs as robust, multifunctional platforms for sustainable catalysis involving CO₂ fixation and C–N bond formation.