Metal–organic frameworks (MOFs) exhibit an exceptional surface area-to-volume ratio, variable pore sizes, and selective binding, and hence, there is an ongoing effort to advance their processability for broadening their utilization in different applications. In this work, we demonstrate a general scheme for fabricating freestanding MOF-embedded polymeric fibers, in which the fibers themselves act as microreactors for the in situ growth of the MOF crystals. The MOF-embedded fibers are obtained via a two-step process, in which, initially, polymer solutions containing the MOF precursors are electrospun to obtain microfibers, and then, the growth of MOF crystals is initiated and performed via antisolvent-induced crystallization. Using this approach, we demonstrate the fabrication of composite microfibers containing two types of MOFs: copper (II) benzene-1,3,5-tricarboxylic acid (HKUST-1) and zinc (II) 2-methylimidazole (ZIF-8). The MOF crystals grow from the fiber’s core toward its outer rims, leading to exposed MOF crystals that are well rooted within the polymer matrix. The MOF fibers obtained using this method can reach lengths of hundreds of meters and exhibit mechanical strength that allows arranging them into dense, flexible, and highly durable nonwoven meshes. We also examined the use of the MOF fiber meshes for the immobilization of the enzymes catalase and horse radish peroxidase (HRP), and the enzyme-MOF fabrics exhibit improved performance. The MOF-embedded fibers, demonstrated in this work, hold promise for different applications including separation of specific chemical species, selective catalysis, and sensing and pave the way to new MOF-containing performance fabrics and active membranes.

Fracture formation due to drying is a common process in a range of systems, from mud cracks to thin polymeric films. Design and control of the fracturing process can be used as a tool for directing the fractures into predefined paths, leading to patterning and controlled fragmentation. In this work, we report the spontaneous periodic fragmentation of polymeric microfibers upon drying. The microfibers are fabricated via electrospinning of amphiphilic triblock copolymers over a glass substrate, and throughout their drying, highly periodic and sharp transverse cracking occurs along the fiber, resulting in the production of anisotropic microparticles (MPs) with a remarkably narrow size distribution. The average length of the MPs depends on the fiber's diameter; hence, by tuning the diameter of the fibers, size control over the MPs is achieved. X-ray scattering measurements reveal the formation of a lamellar arrangement of the copolymers along the fiber, providing a molecular insight into the formation of sharp transverse fractures. Adjusting the lipophilicity of the two terminal hydrophobic dendritic blocks of the triblock copolymers allows tuning the solubility of the obtained MPs in water and the release rate of hydrophobic cargo, opening a new route for the fabrication of anisotropic MPs for controlled release applications.

Shape-morphing active networks of mesoscale filaments are a common hierarchical feature in biology for applying forces, transporting materials, and inducing motility with microscale resolution. Synthetic morphing systems of similar dimensions and capabilities hold potential for a range of technological applications, from micro-muscles to shape-morphing optical devices. Here, the fabrication of highly-ordered 2D networks hierarchically constructed of thermoresponsive mesoscale polymeric fibers, which can exhibit morphing with microscale resolution, is presented. It is demonstrated both experimentally and computationally that the morphing of such networks strongly depends on the physical attributes of the single fiber, in particular on two intrinsic length scales-the fiber diameter and mesh size, which stems from network's density. It is shown that depending on these parameters, such fiber-networks exhibit one of two thermally driven morphing behaviors: i) the fibers stay straight, and the network preserves its ordered morphology, exhibiting a bulk-like behavior; or ii) the fibers buckle and the network becomes messy and highly disordered. Notably, in both cases, the networks display memory and regain their original ordered morphology upon shrinking. This hierarchically induced phase transition, demonstrated here on a range of networks, offers a new way of controlling the shape-morphing of synthetic materials with mesoscale resolutions.

A key aspect of the use of conventional fabrics as smart textiles and wearable electronics is to incorporate a means of electrical conductivity into the single polymer fibre. We present...