To achieve a successful C(sp 3 )-H functionalization reaction in continuous flow with inline catalyst recycling via nanofiltration, suitable commercial membranes were initially evaluated. While the large molecular weight and stability of TBADT make it an ideal candidate for membrane-based recovery, its poor solubility in solvents other than acetonitrile and acetone represents a significant challenge due to the limited compatibility of commercial OSN membranes with such solvents. Commercial membranes were screened using a Zaiput 10 cross-flow cell and by measuring the flux and selectivity during filtration of 1 mM TBADT solutions in acetonitrile (see Supplementary Information, section 2.1, Figure ). Of the membrane pool taken into consideration, only NF080105 and NF030306 from SolSep BV could withstand filtration experiments in acetonitrile. Therefore, these membranes were chosen for further testing involving longer experiment times and higher pressures, which highlighted the unsuitability of NF080105 due to a high failure rate during prolonged filtration experiments paired with issues of catalyst accumulation in the membrane, which negatively affected the membrane flux and mass balance during the filtration (Supplementary Information, Section 2.5, Figure ). Therefore, the outcome of the membrane screening was that NF030306 is a suitable membrane for OSN of acetonitrile solutions containing TBADT. An important consideration is that the high chemical resistance of this membrane comes at the expense of a relatively low membrane flux, resulting in a limited permeate-to-retentate ratio. However, this issue can be obviated with an appropriate design of the filtration stages, as shown in the discussion below.