Chiral Polyaniline Helical Nanotubes Immobilized with Pd Nanoparticles for Enantioselective Catalysis

The precise synthesis of chiral helical nanotubes and the fundamental understanding of how they dictate catalytic enantioselectivity represent pivotal challenges in the field of enantioselective catalysis. Herein, we report a template-assisted strategy for constructing right- and left-handed polyaniline (P- and M-PANI) helical nanotubes. This platform enables the straightforward engineering of chiral nanozymes through the integration of palladium (Pd) nanocubes (Pd_c) and Pd nanoicosahedrons (Pd_i). The resulting P-PANI-Pd_c/Pd_i and M-PANI-Pd_c/Pd_i exhibit catalytic enantioselectivity that is dually dependent on both the supramolecular chirality of PANI helical nanotubes and the crystal facet of Pd-based nanoparticles. Accordingly, P-PANI-Pd_c/Pd_i nanozymes preferentially oxidize 3,4-dihydroxy-S-phenylalanine (S-DOPA) with selectivity factors of 2.54 and 2.24. In contrast, their M-PANI counterparts favor R-DOPA, showing selectivity factors of 2.68 and 2.30. Mechanistic studies revealed that this enantioselectivity stems from more efficient adsorption of the preferred substrate. Furthermore, we show that the enantioselectivity difference originating from Pd_c and Pd_i is directly attributable to their crystal facet-dependent adsorption behaviors. This work establishes an effective route to chiral nanotubes and provides a fundamental link between the nanoscale surface structure and macroscopic chiral performance.