Noncovalent Peptide Assembly Enables Crystalline, Permutable, and Reactive Thiol Frameworks

Though thiols are exceptionally versatile, their high
reactivity
has also hindered the synthesis and characterization of well-defined
thiol-containing porous materials. Leveraging the mild conditions
of the noncovalent peptide assembly, we readily synthesized and characterized
a number of frameworks with thiols displayed at many unique positions
and in several permutations. Importantly, nearly all assemblies were
structurally determined using single-crystal X-ray diffraction to
reveal their rich sequence–structure landscape and the cooperative
noncovalent interactions underlying their assembly. These observations
and supporting molecular dynamics calculations enabled rational engineering
by the positive and negative design of noncovalent interactions. Furthermore,
the thiol-containing frameworks undergo diverse single-crystal-to-single-crystal
reactions, including toxic metal ion coordination (e.g., Cd2+, Pb2+, and Hg2+), selective uptake of Hg2+ ions, and redox transformations. Notably, we find a framework
that supports thiol–nitrosothiol interconversion, which is
applicable for biocompatible nitric oxide delivery. The modularity,
ease of synthesis, functionality, and well-defined nature of these
peptide-based thiol frameworks are expected to accelerate the design
of complex materials with reactive active sites.