Photoregeneration of NADH Using Carbon-Containing TiO₂

A novel photochemical approach for NADH regeneration, which employs visible light as a light source, carbon-containing TiO 2, and [Cp*Rh(bpy)(H 2 O)] 2+ as a catalyst, has been developed here. The carbon-containing TiO 2 has a strong absorption toward visible light. [Cp*Rh(bpy)(H 2 O)] 2+ shows high activity and selectivity toward 1,4-NADH. In the photoregeneration of NADH, the conversion is low and only achieves 25.83% at 31 °C and pH 6.5 when using H 2 O as an electron donor. While under the same conditions using mercaptoethanol, the conversion achieves 74.30% and even reaches 94.29% in the presence of H 2 . Lower pH and higher temperature result in higher conversion and a higher reaction rate. The influence of the initial concentration of [Cp*Rh(bpy)(H 2 O)] 2+ on NADH photoregeneration is much greater than that of the initial concentration of NAD + . The optimum conditions for NADH photoregeneration are determined to be a pH of 6.0, 37 °C, a NAD + initial concentration of 0.2 mM, and a [Cp*Rh(bpy)(H 2 O)] 2+ initial concentration of 0.3∼0.5 mM. The conversion achieves 63.98% under optimum conditions.