Electrospinning of Metal–Organic Frameworks for Energy and Environmental Applications

Abstract

organic linkers with a periodic, nanoscaled structure and ultrahigh surface areas. With their tunable pore/cage sizes, flexible skeleton, and large surface-to-volume ratio, [13][14][15][16][17][18][19] MOFs have a large potential for a wide range of applications, including gas storage and separation, rechargeable batteries, supercapacitors, solar cells, nanoreactors, heterogeneous catalysis, or drug delivery. [20][21][22][23][24][25][26][27] Recently, significant efforts have been devoted to the design and synthesis of new MOFs structures and the investigation of their physical or chemical properties. MOFs are generally prepared as bulk form through traditional hydrothermal or solvothermal synthesis. [28][29][30][31] In order to expand the application range, suitable pathways for the structuring of MOF powders into a functional architecture or devices are highly desirable.Currently, intensive efforts are focusing on the structuring of MOFs at the mesoscopic/macroscopic scale for the use as coatings, membranes, or sophisticated architectures in specific devices and applications. [32][33][34][35] A major difference in the structuring of MOFs into complex shapes compared to inorganic microporous materials, such as zeolites or silica, is the fact that most inorganic binders cannot be used for MOFs as these binders usually require heat treatment. The intrinsic fragility of MOFs needs to be considered which is related to the inorganic/organic hybrid character of this class of materials and the resulting limited thermal and mechanical stability. Alternatively, a more effective way to structure MOFs is the combination with polymer materials. The polymer which acts as a binder improves the mechanical flexibility and ensures chemical stability. Numerous methods have been developed for structuring MOF-polymer compositions including hard or soft templates, spin-or dip-coating, spray-drying, printing, or lithography approaches. [36][37][38] The integration of MOFs into a polymer matrix can result in poor MOF-polymer dispersion and compatibility issues owing to the different physical and chemical properties for the two kinds of materials and this is a challenge in some applications, e.g., in MOF-based mixed matrix membranes for gas separation. [39][40][41][42] The poor interfacial compatibility would lead to agglomeration of MOF particles, causing the formation of nonselective voids between the MOFs particles and the polymer.Electrospinning is a fabrication method to produce continuous ultrafine fibers with diameters in the range of a few tens of nanometers to a few micrometers in the form of nonwoven mats, yarns, etc. The mechanism of electrospinning is based Herein, recent developments of metal-organic frameworks (MOFs) structured into nanofibers by electrospinning are summarized, including the fabrication, post-treatment via pyrolysis, properties, and use of the resulting MOF nanofiber architectures. The fabrication and post-treatment of the MOF nanofiber architectures are described systematically by two routes: i) the dire...

One-Dimensional (1D) Nanostructured Materials for Energy Applications

“…Unlike top-down techniques, the “bottom-up” approach is based on molecular recognition and chemical self-assembly of molecules, which allows obtaining structures with sizes that can vary from a few nanometers to several microns. This approach, in turn, includes different methodologies, among which it is worth mentioning vapor-phase growth [ 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 ], liquid-phase growth [ 51 , 52 ], template-assisted etching [ 53 , 54 , 55 , 56 , 57 ], and electrospinning [ 58 , 59 , 60 , 61 , 62 ].…”

An Overview of Oxygen Reduction Electrocatalysts for Rechargeable Zinc-Air Batteries Enabled by Carbon and Carbon Composites

“…[52][53][54][55][56][57][58][59][60][61][62][63][64] Compared with traditional bulk materials, the samples with regular morphologies show higher specific surface area, lower agglomeration and greater structural stability, and thus possess practical application values. [65] Generally, the influence of material structures on the electrochemical performance of metal-air batteries are manifold. For example, the ultra-high specific surface area and porosity of the material can ensure excellent dispersion of catalyst and provide more reactive sites, and simultaneously improve the adsorption rate and diffusion permeability of the O2.…”

One-dimensional (1D) Nanostructured Materials for Energy Applications

“…Unlike top-down techniques, the "bottom-up" approach is based on molecular recognition and chemical self-assembly of molecules, which allows obtaining structures with sizes that can vary from a few nanometers to several microns. This approach, in turn, includes different methodologies, among which it is worth mentioning vapor-phase growth [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50], liquid-phase growth [51,52], template-assisted etching [53][54][55][56][57], o electrospinning [58][59][60][61][62].…”