A bimetallic-MOF catalyst for efficient CO2photoreduction from simulated flue gas to value-added formate

Direct CO(2)conversion from flue gas into high-value products is of great significance not only in relieving environmental burden but alleviating the energy crisis by a low-cost and energy-saving avenue, yet few studies in this aspect have been reported. Herein, we report metal-node-dependent catalytic performance for solar-energy-powered CO(2)reduction to formate in simulated flue gas by bimetallic Ni/Mg-MOF-74. The yield of HCOO(-)with Ni0.75Mg0.25-MOF-74 as a catalyst in pure CO(2)is 0.64 mmol h(-1)g(MOF)(-1)which is higher than that of Ni-MOF-74 (0.29 mmol h(-1)g(MOF)(-1)) and Ni0.87Mg0.13-MOF-74 (0.54 mmol h(-1)g(MOF)(-1)), whereas monometallic Mg-MOF-74 is almost inactive, indicating that reactivity relies on metal nodes. In simulated flue gas without water vapor at 20 degrees C, similar to 80% of the reactivity in pure CO(2)is retained, with HCOO(-)generation reaching 0.52 mmol h(-1)g(MOF)(-1). This activity is comparable to that of the best MOF catalysts in pure CO2, demonstrating that Ni/Mg-MOF-74 not only overcomes the limitation from CO(2)concentration, but also has good resistance to other gas components in flue gas at 20 degrees C. DFT calculations reveal the high output for HCOO(-)from two crucial factors: strong CO(2)binding affinity of Mg sites, and the synergistic effect of Mg and Ni leading to the stabilization of the key *OCOH intermediate with an appropriate energy barrier. This work paves a new route for double-metal MOFs to enhance the CO(2)photoreduction reactivity in flue gas.