Development of an Integrated System for Highly Selective Photoenzymatic Synthesis of Formic Acid from CO2

Graphical Tailor made ! An environmentally friendly and highly effective semi-artificial photosynthetic system (FDH@Rh-TCPP-UiO-66-NH 2 ) was developed for transforming CO 2 into formic acid. The incorporation of NADH-dependent formic acid dehydrogenase (FDH), photosensitive porphyrin ligands and Rh complex lead to highly selective and recyclable system. Herein, a Zr-based dual-ligand MOFs with pre-installed Rh complex was employed for NADH regeneration in situ and also used for immobilization of formic acid dehydrogenase (FDH) in order to realize a highly efficient CO 2 fixation system. Then, based on the detailed investigations into the photochemical and electrochemical properties, it is demonstrated that the introduction of the photosensitive meso-tetra(4-carboxyphenyl) porphin (TCPP) ligands increased the catalytic active sites and improved photoelectric properties. Furthermore, the electron mediator Rh complex, anchored on the zirconium-based dual-ligand MOFs, enhanced the efficiency of electron transfer efficiency and facilitated the separation of photogenerated electrons and holes. Compared with UiO-66-NH 2 , Rh-H 2 TCPP-UiO-66-NH 2 exhibits an optimized valence band structure and significantly improved photocatalytic activity for NAD + reduction, resulting the synthesis of formic acid from CO 2 increased from 150 μg mL −1 (UiO-66-NH 2 ) to 254 μg mL −1 (Rh-H 2 TCPP-UiO-66-NH 2 ). Moreover, the assembled photocatalyst-enzyme coupled system also allows facile recycling of expensive electron mediator, enzyme, and photocatalyst.