(560bi) Artificial Thylakoid to Coordinate Photo-Enzyme-Coupled Catalysis for Carbon Dioxide Upgrading

Shaohua Zhang^a,c, Jiafu Shi^b,c, Zhongyi Jiang ^b,c

^a Key Laboratory for Green Technology of Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China

^b School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China

^c Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300072, China

Artificial photosynthesis has become the hotspot in energy and environmental relevant fields. Generally speaking, the well-defined catalyst and the well-organized complex reaction system jointly determine the efficiency of artificial photosynthesis process. Currently, most efforts are devoted to the intensive exploitation of efficient catalysts, while less efforts are devoted to the rational construction of artificial photosynthesis system by coordinately manipulating different catalytic reactions therein.

Inspired by thylakoid in chloroplast, we explore a capsular structure to coordinate photocatalysis and biocatalysis for the construction of artificial photosynthesis system. The capsular structure, termed as artificial thylakoid, has a wall composed of cadmium sulfide quantum dots shielded by an amorphous titania wall. The artificial thylakoid could absorb visible light to activate the single- and multiple-enzymatic CO₂ reduction by oriented transfer of photo-generated electrons through the capsule wall for NADH regeneration. The photo-generated holes and its reactive oxygen species are ‘imprisoned’ in the lumen of the artificial thylakoid, avoiding its poison effect on the enzymes in solution. The artificial thylakoid affords a compatible design strategy to coordinate photocatalysis and biocatalysis of the photo-enzymatic system. Under visible light illumination, CO₂ is converted to formate and methanol with a production rate of 1500 μM h^-1 and 99 μM h^-1 that were much higher than previous particulate photo-enzymatic systems. Moreover, CO₂ can be converted to formate over several light-dark cycles with a quantum yield of 0.66±0.13%, comparable to the year-long average determined for natural green plants (~0.2 to 1.6%).