Electrochemiluminescent Enantiodiscrimination on Chiral Engineered l-His-ZIF8

The development of highly efficient chiral recognition systems by simple and cost-effective means is critical to advance the precise application of chiral molecules. Herein, a novel electrochemiluminescence (ECL) enantioselective recognition platform was constructed based on l-histidine-functionalized zeolitic imidazolate frameworks (l-His-ZIF8). Detailed characterization verified the successful preparation of the chiral l-His-ZIF8 material. It was then applied to the chiral discrimination of six amino acids: cysteine (Cys), tryptophan (Trp), phenylalanine (Phe), glutamic acid (Glu), histidine (His), and proline (Pro). Among them, the system employing Ru(bpy)₃²⁺ as the luminophore demonstrated the most efficient chiral recognition of d-Cys over l-Cys, as evidenced by a distinct ECL signal ratio (ECLd-Cys/ECLl-Cys) of 3.3 at 1 mM. A detection limit of approximately 0.193 mM was achieved for Cys enantiomers. Conversely, an inverse chiral recognition was observed for the tryptophan (Trp)/sodium tetraphenylborate (TPB) system, resulting in a stronger ECL response for l-Trp over that for d-Trp (ECLl-Trp/ECLd-Trp = 2.4 at 1 mM). Theoretical calculations indicate that the excellent ECL enantioselectivity stems from the preferential binding of the "host" l-His-ZIF8 with specific "guest" enantiomers (d-Cys or l-Trp) via stronger intermolecular interactions. This preferential binding leads to the formation of more stable diastereoisomers that facilitate electrooxidation of more "guests" to generate a stronger luminescent signal than its isomer. This study establishes a novel strategy for electrochemiluminescent enantiomer discrimination using chiral site-engineered metal-organic frameworks (MOFs) and opens new avenues for the future of chiral sensing.