Photo-induced enzymatic conversion of CO2 gas to solar fuel on functional cellulose nanofiber films
Functional cellulose nanofiber films for the production of solar fuel from CO2 gas were prepared by immobilizing dendrimer and porphyrin derivative and loading an electron donor and enzymes (formate, aldehyde and alcohol dehydrogenases) on the films. Porphyrin derivative is a photosensitizer and dendrimer plays a role of the reservoir of guest gases and the carrier of electron/proton besides of the intermediation for binding of porphyrin derivative on nanofiber. Desorption of CO2 gas without laser irradiation was almost half of adsorption. However, the remained gas amount after laser irradiation was almost half of that without laser irradiation on a film without an electron donor and enzymes but it was almost equal to or slightly higher than that without laser irradiation on films with an electron donor and enzymes. These results suggest the conversion of CO2 gas under laser irradiation. The conversion efficiency from CO2 to formic acid was only half because of the possible reaction of only CO2 in vicinity of reaction system, but the efficiencies from formic acid to formaldehyde and from formaldehyde to methanol were ~80 and ~90 wt%, indicating the successful stepwise conversion by photo-induced enzyme reaction.