Zr-based metal-organic frameworks (MOFs) are promising supports for copper-based catalysts able to activate methane. Homo- and heterobimetal-functionalized NU-1000 MOF nodes were selected to computationally screen the effect of ancillary metals for C-H bond activation, allowing us to correlate activation free energies with chemical descriptors.

A novel method for controlling the oligomerization of metastable DNA hairpins using the hybridization chain reaction (HCR) is reported. Control was achieved through the introduction of a base-pair mismatch in the duplex of the hairpins. The mismatch modification allows one to kinetically differentiate initiation versus propagation events, leading to DNA oligomers up to 10 monomers long and improving dispersities from 2.5 to 1.3–1.6. Importantly, even after two consecutive chain extensions, dispersity remained unaffected, showing that well-defined block co-oligomers can be achieved. As a proof-of-concept, this technique was then applied to hairpin monomers functionalized with a mutant green fluorescent protein to prepare protein oligomers. Taken together, this work introduces an effective method for controlling living macromolecular HCR oligomerization in a manner analogous to the controlled polymerization of small molecules.

CONSPECTUS: Proteins are a class of nanoscale building block with remarkable chemical complexity and sophistication: their diverse functions, shapes, and symmetry as well as atomically monodisperse structures far surpass the range of conventional nanoparticles that can be accessed synthetically. The chemical topologies of proteins that drive their assembly into materials are central to their functions in nature. However, despite the importance of protein materials in biology, efforts to harness these building blocks synthetically to engineer new materials have been impeded by the chemical complexity of protein surfaces, making it difficult to reliably design protein building blocks that can be robustly transformed into targeted materials. Here we describe our work aimed at exploiting a simple but important concept: if one could exchange complex protein−protein interactions with well-defined and programmable DNA−DNA interactions, one could control the assembly of proteins into structurally well-defined oligomeric and polymeric materials and three-dimensional crystals. As a class of nanoscale building block, proteins with surface DNA modifications have a vast design space that exceeds what is practically and conceptually possible with their inorganic counterparts: the sequences of the DNA and protein and the chemical nature and position of DNA attachment all play roles in dictating the assembly behavior of protein−DNA conjugates. We summarize how each of these design parameters can influence structural outcome, beginning with proteins with a single surface DNA modification, where energy barriers between protein monomers can be tuned through the sequence and secondary structure of the oligonucleotide. We then explore challenges and progress in designing directional interactions and valency on protein surfaces. The directional binding properties of protein−DNA conjugates are ultimately imposed by the amino acid sequence of the protein, which defines the spatial distribution of DNA modification sites on the protein. Through careful design and mutagenesis, bivalent building blocks that bind directionally to form one-dimensional assemblies can be realized. Finally, we discuss the assembly of proteins densely modified with DNA into crystalline superlattices. At first glance, these protein building blocks display crystallization behavior remarkably similar to that of their DNA-functionalized inorganic nanoparticle counterparts, which allows design principles elucidated for DNA-guided nanoparticle crystallization to be used as predictive tools in determining structural outcomes in protein systems. Proteins additionally offer design handles that nanoparticles do not: unlike nanoparticles, the number and spatial distribution of DNA can be controlled through the protein sequence and DNA modification chemistry. Changing the spatial distributions of DNA can drive otherwise identical proteins down distinct crystallization pathways and yield building blocks with exotic distributions of DNA that crystallize into structures that ar...

Postsynthetic metal exchange represents a powerful synthetic method to generate metal-organic frameworks (MOFs) that are not accessible through direct synthesis, yet it is often hampered by slow reaction kinetics and incomplete exchange. While studies of metal exchange reactions have primarily focused on the transmetalation process, transport of exogenous metal ions into the framework structure represents a critical yet underexplored process. Here, we employ X-ray crystallography, electron microscopy, and energy dispersive X-ray spectroscopy to comprehensively examine the transport of Co and Zn ions during postsynthetic metal exchange reactions within the 2D manganese-benzoquinoid framework (EtN)[MnL] (HL = 3,6-dichloro-2,5-dihydroxy-1,4-benzoquinone). These studies reveal that exogenous metal ions diffuse primarily through the 1D channel along the crystallographic c axis, and this transport represents the rate-determining step. In addition, the Mn framework exhibits reversible dynamic structure behavior, contracting upon desolvation and then rapidly restoring its original structure and full volume upon resolvation. When conducting metal exchange reactions using a partially desolvated sample, these structural dynamics lead to acceleration of metal transport by up to 2000-fold, improve product purity, and give exchange of a larger fraction of metal sites. Finally, upon performing metal exchange using full-solvated crystals, an intermediate product can be isolated that constitutes a unique example of a 2D material with a gradient vertical heterostructure.