This study demonstrates a novel method to quantify selective (1,4-NADH) and unselective products (1,2- and 1,6-NADH) in NADH regeneration using combined UV-Vis spectroscopy and biological assays.

This study shows the importance of resolving catalytic performance in the regeneration of the reduced form of nicotinamide adenine dinucleotide (NADH) through activity measurements based on NAD+ conversion and the closure of mass balance via byproduct quantification. This approach is applied to assess the performance of supported platinum catalysts with varying points of zero charge, utilizing H2 as a reductant. It was found that Pt/SiO2, which exhibits a net negative charge under the reaction conditions, outperforms the neutral Pt/C and positively charged Pt/MgO because of the favorable electrostatic attraction between the catalyst surface and positively charged (+1) nicotinamide ring. NMR spectroscopy identifies side-products formed during NAD+ hydrogenation.

A series of ceria–zirconia mixed metal oxides with varying metal ratios were prepared by the calcination of precursors synthesized by mechanochemical grinding of the metal carbonates, and tested for catalytic naphthalene and propane total combustion. The mechanically-mixed metal oxides were more active for both propane and naphthalene total oxidation compared to the parent metal oxides. Ce0.95Zr0.05Ox was the most active catalyst for the total combustion of propane and naphthalene. Catalysts were characterized by x-ray diffraction, BET surface area, laser Raman spectroscopy, temperature programmed reduction, scanning electron microscopy with energy dispersive x-ray analysis and x-ray photoelectron spectroscopy techniques. Formation of ceria–zirconia solid solutions was observed for catalysts with a zirconia content of 10% or lower, whereas ceria and zirconia phase separation was observed when zirconia content was above 25%. Surface area increased when ceria and zirconia were mixed, and the reduction temperature of the bulk shifted to lower temperatures upon increasing zirconia content. Incorporation of zirconia was found to increase the relative concentration of surface oxygen defects compared to pure ceria, with low amounts of zirconia showing the greatest increase. The concentration of oxygen defects correlates with propane and naphthalene total oxidation activity. The enhanced total oxidation activity occurs as a result of the increased number of oxygen defects and the higher surface area. The results demonstrate that mechanochemical preparation from carbonate precursors was an effective route to make active catalysts.

The reduced form of nicotinamide adenine dinucleotide (NAD(P)H) behaves as an energy/chemical "currency", carrying hydrogen in a biologically convertible form and donates electrons in numerous biotransformations and artificial photosynthesis. Its high cost necessitates its regeneration for reuse where photocatalysis using light energy is attractive. However, high NAD(P)H yield is only achievable via organic mediators to transfer electrons.Here, we analyse the current issues in catalytic NAD(P)H regeneration and show that a continuous-flow reactor system can realise selective NAD(P)H regeneration with 100% yield using Pt/C3N4 as a photocatalyst.

NAD(P)H is a key cofactor widely used in biocatalytic reductive transformations, facilitating a wide range of industrially significant reactions which ultimately result in the consumption of the costly cofactor. To...