*3.2. Nylon-Based Membranes*

With the aim of solving the diffusion problems observed with PAN nanofibers, Nylon 6,6 (NYL) was thus selected as matrix polymer for catalytic membrane production. Indeed, Nylon 6,6 has a lower glass transition (T<sup>g</sup> <sup>=</sup> 50–60 ◦C) compared to PAN coupled with a high melting temperature (Figure S8). These properties should allow good temperature stability and a slightly higher hydrophilicity with respect to PAN fibers. Stemming from previously obtained results that highlighted better performances for bimetallic systems, nanofibers were produced solely with TiO<sup>2</sup> supported AuPd nanoparticles (NYL + AuPd/TiO2). Together with the reference NPs free fibers (i.e., plain NYL and NYL + TiO2), two additional catalytic membranes were also produced, one containing independently added TiO<sup>2</sup> and unsupported AuPd NPs (NYL + AuPd + TiO2) and the other containing just the unsupported AuPd NPs (NYL + AuPd). The latter two samples aimed at exploring the ability of the nanofibrous polymeric systems to stabilize the metallic nanoparticles and the role of TiO<sup>2</sup> in the complex catalytic medium. While the procedure for adding titania supported AuPd nanoparticles (AuPd/TiO2) was similar to the previously applied method for PAN fibers (with some limitation in particle content due to high-concentration suspension stability issues during the process), addition of unsupported bimetallic NPs was possible due to the solvent system used for nylon electrospinning (formic acid/chloroform) that proved to be slightly water tolerant. Formic acid (FA) was indeed used to replace water as much as possible as NPs solvent (17 wt.% water residual tolerated) with subsequent washing/centrifugation steps that did not alter NPs dimensions or promoted their aggregation (Figures S3 and S4). Such FA suspension was then used in a procedure similar to the one applied for plain nylon nanofibers or to

the procedure for obtaining NYL + TiO<sup>2</sup> nanofiber to attain NYL + AuPd and NYL + AuPd + TiO<sup>2</sup> catalytic membranes respectively.
