Multiple Cuprous Centers Supported on a Titanium-Based Metal–Organic Framework Catalyze CO2 Hydrogenation to Ethylene

Hydrogenation of carbon dioxide (CO2) to ethylene (C2H4) can be achieved in two routes via tandem reactions: (1) CO2 hydrogenation to methanol (CH3OH) followed by methanol-to-olefin conversion and (2) reverse water-gas shift reaction followed by Fischer–Tropsch synthesis. Here we present another tandem route for CO2-to-C2H4 conversion via (3) CO2 hydrogenation to ethanol (C2H5OH) followed by C2H5OH dehydration. Multiple cuprous (CuI) centers were loaded onto the Ti8(μ2-O)8(μ2-OH)4 secondary building units of a Ti-based metal–organic framework (MOF), MIL-125-NH2, via deprotonation and ion exchange of the μ2-OH groups. These multiple CuI centers catalyzed CO2 hydrogenation to C2H5OH, while the Ti2-μ2-O–M+ (M+ = H+, Li+) sites converted C2H5OH to C2H4. The MOF achieved CO2-to-C2H4 generation rates of up to 2598 μmol gCat–1 h–1 in supercritical CO2 (CO2 30 MPa, H2 5 MPa) at 85 °C and 514 μmol gCat–1 h–1 in the gas phase at 5 MPa (H2:CO2 = 3) and 100 °C, respectively. This work opens another path to selectively producing C2H4 via the hydrogenation of CO2.