Membrane-based TBADT recovery: increasing the sustainability of continuous-flow photocatalytic HAT transformations

31 May 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Photocatalytic hydrogen atom transfer (HAT) processes have been the object of numerous studies showcasing the potential of the homogeneous photocatalyst tetrabutylammonium decatungstate (TBADT) for the functionalization of C(sp3)–H bonds. However, to translate these studies into large-scale industrial processes, careful considerations of catalyst consumption, cost, and removal are required. This work presents organic solvent nanofiltration (OSN) as the answer to reduce TBADT consumption, to increase its turnover number and to lower its concentration in the product solution, thus enabling large-scale photocatalytic HAT-based transformations. The operating parameters for a suitable membrane for TBADT recovery in acetonitrile were optimized. Continuous photocatalytic C(sp3)-H alkylation reactions were carried out with in-line TBADT recovery via two OSN steps. Promisingly, the observed product yields for the reactions with in-line catalyst recycling are comparable to those of reactions performed with pristine TBADT, therefore highlighting that not only catalyst recovery (>99%, TON > 6500) is a possibility, but also that it does not happen at the expense of reaction performance.


flow chemistry
hydrogen atom transfer
catalyst recovery
organic solvent nanofiltration
C−H functionalization
homogeneous catalysis

Supplementary materials

Supporting Information
The authors declare that all relevant data supporting the findings of this study are available within the article and Supplementary Information files, and also are available from the corresponding author upon reasonable request.

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