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Artificial photosynthetic system for diluted CO₂ reduction in gas-solid phase
Summary:
The authors from Heilongjiang Provincial Key Laboratory of CO₂ Resource Utilization and Energy Catalytic Materials, School of Material Science and Chemical Engineering, Harbin University of Science and Technology, and School of Chemistry, South China Normal University developed [Emim]BF₄@PCN-250-Fe₂Co, which has high CO₂ adsorption capacity, excellent visible light response, and good stability, achieving efficient reduction of diluted CO₂ to CO in the application of artificial photosynthesis.
Background:
1. To address the challenge of efficiently capturing and converting diluted CO₂ from flue gas, previous researchers explored various photocatalysts such as MOFs and ionic liquids (ILs). While some progress was made, their activity under diluted CO₂ conditions was extremely low, far from practical application.
2. The authors in this study proposed integrating CO₂-enriching ILs with photoactive MOFs PCN-250-Fe₂M to construct host-guest photocatalysts, and obtained high CO₂ reduction activity even under diluted CO₂ atmosphere.
Research Content:
1. Synthesis:
The authors synthesized PCN-250-Fe₂M via solvothermal reaction using preformed Fe₂M clusters and 3,3′,5,5′-azo-benzene tetra-carboxylic acid ligand with acetic acid as a competing reagent. Then, [Emim]BF₄ was introduced into the pores of PCN-250-Fe₂Co by dispersing in anhydrous ethanol and stirring with PCN-250-Fe₂Co, followed by drying to obtain [Emim]BF₄@PCN-250-Fe₂Co.
2. Characterizations:
1) BET results showed that PCN-250-Fe₂Co had a surface area of 960.8 m²g⁻¹, which decreased to 482.6 m²g⁻¹ after loading [Emim]BF₄; pore size distribution showed a decrease from 0.82 nm to 0.48 nm after loading.
2) SEM/TEM tests show the particle size of the material: PCN-250-Fe₂Co exhibits polyhedral shape with a particle size of ~10 μm, and [Emim]BF₄@PCN-250-Fe₂Co has a similar morphology with uniform distribution of elements.
3) Other tests: UV-vis DRS showed PCN-250-Fe₂Co has a band gap of 1.85 eV; XPS confirmed the presence of Fe, Co, C, N, O, B, and F elements in the composite; TGA indicated both materials are stable up to 350 °C; CO₂ adsorption test showed [Emim]BF₄(39.3 wt%)@PCN-250-Fe₂Co has a CO₂ adsorption capacity of 87.3 cm³g⁻¹ at 298 K, ~1.88 times higher than PCN-250-Fe₂Co.
3. Application:
The material was tested in CO₂ photoreduction. Under pure CO₂, [Emim]BF₄(39.3 wt%)@PCN-250-Fe₂Co achieved a CO evolution rate of 313.34 μmol g⁻¹h⁻¹; under diluted CO₂ (15%), it reached 153.42 μmol g⁻¹h⁻¹ with ~100% selectivity. In scaled-up experiments under natural sunlight, it reduced CO₂ concentration effectively, showing industrial application potential.
4. Mechanism:
[Emim]BF₄ enriches and activates CO₂, forming Emim-CO₂. The synergistic effect between [Emim]BF₄ and Co²⁺ sites in PCN-250-Fe₂Co transfers activated CO₂ to Co²⁺, reducing the Gibbs free energy barrier of the rate-determining step (*COOH-Emim formation). Co²⁺ acts as the active site for CO₂ reduction, and Fe³⁺ for H₂O oxidation, achieving the overall artificial photosynthetic reaction.
Outlook:
This research develops a host-guest synergistic system for efficient diluted CO₂ reduction, providing a universal strategy and mechanistic insights for artificial photosynthetic CO₂ conversion, with great potential for industrial applications.
Artificial photosynthetic system for diluted CO₂ reduction in gas-solid phase
Authors: Ya Wang, Jian-Xin Wei, Hong-Liang Tang, Lu-Hua Shao, Long-Zhang Dong, Xiao-Yu Chu, Yan-Xia Jiang, Gui-Ling Zhang, Feng-Ming Zhang, Ya-Qian Lan
DOI: 10.1038/s41467-024-53066-y
Link: https://www.nature.com/articles/s41467-024-53066-y
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