Cadmium sulfide nanoparticles compositing with chitosan and metal-organic framework: Enhanced photostability and increased carbon dioxide reduction

The utilization of photocatalytic enzyme-coupled systems is considered a promising solution to the solar energy conversion challenge, but it is hampered by its low cofactor regeneration efficiency. Herein, a biomimetic catalytic system was designed inspired by photosynthesis for cofactor regeneration and CO 2 reduction. The Rh complexes were anchored in the core of metal-organic framework UiO67 and chitosan (CS) on the UiO67@Rh surface skillfully helped the in situ growth of CdS. In this core-shell nanoreactor, UiO67@Rh accepted the electrons produced by CdS for cofactor regeneration. CS acted as a bifunctional bio-scaffold to attach CdS and prevent CdS photocorrosion. Besides, CS spatially separated Rh complexes and CdS, preventing deactivation of Rh complexes by CdS and leakage of Rh complexes. Surprisingly, CS improved the photocatalytic activity and photostability of CdS, while other biomacromolecules did not have this function. The photocatalyst regeneration NADH cooperated with formate dehydrogenase (FDH) for CO 2 reduction. The results showed that 0.72 mM formic acid was produced in 5 h (TOF = 0.14 mmol/mg/h), which was triple as much as in the system of UiO67@Rh@CdS and FDH. This cyclic process could be repeated up to 10 time cycles, where long-term stability of the system was observed and the active state of the enzymes was preserved. This study demonstrated a new and promising organometallic photocatalyst-based artificial cofactor regeneration system, paving the path for further research into the bespoke synthesis of fine chemicals and solar fuels from CO 2 utilizing solar energy. Graphical abstract CdS nanoparticles compositing with chitosan and metal-organic frameworks for cofactor regeneration and CO 2 reduction