Assessing the environmental performance of NADH regeneration methods: A cleaner process using recyclable Pt/Fe3O4 and hydrogen.

• NAD(P)H regeneration cleanliness is crucial for sustainable biotransformations. • First assessment of environmental impact of NAD(P)H regeneration methods. • Heterogeneous catalysis and electrocatalysis produce the lowest amount of waste. • Recyclable heterogeneous Pt/Fe 3 O 4 catalyst exhibits an E-factor of ∼1 using H 2. Cofactor (reduced) Nicotinamide Adenine Dinucleotide (NAD(P)H) is an energy carrier in enzymatic redox reactions that are employed for the synthesis of valuable chemicals and pharmaceuticals. The high cost of NAD(P)H makes it impractical to use in stoichiometric amounts in industrial processes. This has led to the development of a variety of methods for NAD(P)H regeneration. In this work, process cleanliness of the current NADH recycling systems was evaluated using E-factor (kg waste /kg NADH) as a green chemistry metric. The E-factor obtained, depending on the process method, reaches values higher than 20000, where non-recyclable agents, including sacrificial hydride/electron donors, catalysts and electron mediators, alongside by-products (from cosubstrates), account for the overall waste. A promising alternative methodology for NADH regeneration using H 2 and recyclable Pt/Fe 3 O 4 is presented and characterisation performed by temperature-programmed reduction (TPR), nitrogen adsorption (surface area/porosity), powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) is used to elucidate the observed performance. The Pt/Fe 3 O 4 system at room temperature delivers a turnover frequency of 20 h−1 and the catalyst can be recycled for reuse, producing a significantly low level of waste (E-factor = ∼1). [ABSTRACT FROM AUTHOR]