Synergistic active sites in nanoscale metal-organic framework catalyst for tandem CO2 and styrene conversion

With the growing demand for sustainable solutions to environmental issues, the efficient conversion of CO 2 into value-added products has become a critical focus. The one-pot tandem synthesis of cyclic carbonates from CO 2 and styrene offered a cost-effective and environmentally friendly approach by streamlining the process and minimizing waste without intermediate separation. However, this method required catalysts with multiple active sites to achieve high efficiency and selectivity. Titanium-based metal-organic frameworks (MOFs), due to their unique electronic structures and active sites, provide distinct advantages in catalysis but face challenges related to synthesis and structural stability. This study synthesized a synergistic Cu-NH 2 -MIL-125 catalyst by chelating Cu ions to amino groups on the ligand via post-synthetic modification (PSM). This catalyst exhibited excellent performance in the tandem reaction of styrene and CO 2 to cyclic carbonates, achieving a 96.4 ​% conversion and 83.9 ​% yield under mild conditions (80 ​°C, 1 ​bar, 16 ​h) without the need for co-catalysts and solvents. This significantly outperformed the parent NH 2 -MIL-125. Incorporating Cu ions enhanced CO 2 adsorption, modulated the electronic environment, and increased the variety of active sites, contributing to improved catalytic efficiency. Cu-NH 2 -MIL-125 catalyst also demonstrated good cyclic stability over four cycles and broad substrate applicability to various styrene derivatives, yielding 74.9 ​% to 81.7 ​%. Furthermore, free radical quenching experiments and molecular simulations suggested that Ti (Ⅳ) promoted free radical formation, Cu(Ⅰ) facilitated styrene oxidation, and NH 2 groups activated CO 2 , collectively driving the one-pot reaction mechanism.