Spatial Organization of Photocatalysts and Enzymes on Janus-Type DNA Nanosheets for Efficient CO2 Conversion

Bioinspired photosynthetic systems composed of photocatalysts and enzymes are a notable framework for converting CO2 to high-value chemicals. However, catalyst/enzyme deactivation and poor electron transfer kinetics in multistep photochemical processes severely limit their catalytic efficiencies. In this study, Janus-type DNA nanosheets (NSs) presenting two different DNA sequences on each face were utilized as a support for the selective immobilization of a Rh complex and formate dehydrogenase (FDH) for concerted catalytic reactions for CO2 reduction. Based on the face selectivity, DNA-conjugated Rh complex and FDH were immobilized on NSs into four different configurations: Rh complex on NS (NS1), FDH on NS (NS2), Rh complex and FDH on opposite faces of NS (NS3), FDH and Rh complex on the same face of NS (NS4). The catalytic system exhibited CO2 conversion efficiencies highly dependent on the spatial organization of Rh complex and FDH, showing the reactivity for the formate production in the order of NS1 coupled with free FDH > NS3 > NS2 coupled with free Rh complex > NS4 > free Rh complex and FDH. The NS1 coupled with free FDH showed turnover number (TON) of 1360 for the formate production based on NAD+, which is the highest value reported thus far for Rh-based photocatalyst/enzyme coupled systems. The results demonstrate that the compartmentalization of photocatalysts and biological enzymes is a viable approach for improving the efficiency of CO2 conversion and provide important design rules for building efficient artificial photosynthetic systems.