Chirality-Dependent Copper–Diphenylalanine Assemblies with Tough Layered Structure and Enhanced Catalytic Performance

Chiral
regulation to prepare functional materials has aroused considerable
interest in recent years. However, little is known on the effect of
chirality of ligands in the metal–organic coordination assembly
process. We report the self-assembly of diphenylalanine peptide (Phe-Phe,
FF), the core fragment of Aβ protein, with metal copper ion
(Cu2+) into metal–organic assemblies with chirality-encoded
structures and properties. The chirality-dependent metal–dipeptide
assembles with different morphologies and supramolecular chirality
were obtained by facile changing of the FF chirality. Single-crystal
results indicate that (L)-FF coordinated with Cu2+ into
a cross-chain structure with a five-coordinated style, while the racemates
of (L+D)-FF with Cu2+ crystallized into an (L)-Cu2+-(D)-Cu2+ alternated four-coordinating structure, enabling
a higher mechanical and catalytic performance. The Young’s
modulus of (L+D)-FF-Cu is as high as 34.36 GPa, which is 2.45 times
higher than that of (L)-FF-Cu. Furthermore, both of them follow the
characteristic enzyme kinetics and show higher catalytic activity
than natural laccase at the same mass concentration. Specifically,
the calculated catalytic efficiency (kcat/KM) of (L+D)-FF-Cu is 1.14 times higher
than that of (L)-FF-Cu, and the (L+D)-FF-Cu shows significantly enhanced
stability and reusability compared with (L)-FF-Cu. The results reveal
that highly functional materials could be constructed by encoding
the chirality of molecular building blocks.