Exploration of Hierarchical Metal–Organic Framework as Ultralight, High-Strength Mechanical Metamaterials

Abstract

Due to the extraordinarily high surface to volume ratio and enormous structural and chemical diversities, metal–organic frameworks (MOFs) have drawn much attention in applications such as heterogeneous catalysis, gas storage separation, and drug delivery, and so on. However, the potential of MOF materials as mechanical metamaterials has not been investigated. In this work, we demonstrated that through the concerted effort of molecular construct and mesoscopic structural design, hierarchical MOFs can exhibit superb mechanical properties. With the cutting-edge in situ transmission and scanning electron microscope (TEM and SEM) techniques, the mechanical properties of hollow UiO-66 octahedron particles were quantitatively studied by compression on individual specimens. Results showed that the yield strength and Young’s modulus of the hierarchical porous framework material presented a distinct “smaller is stronger and stiffer” size dependency, and the maximum yield strength and Young’s modulus reached 580 ± 55 MPa and 4.3 ± 0.5 GPa, respectively. The specific strengths were measured as 0.15 ± 0.03 to 0.68 ± 0.11 GPa g–1 cm3, which is comparable to the previously reported state-of-the-art mechanical metamaterials like glassy carbon nanolattices and pyrolytic carbon nanolattices. This work revealed that MOF materials can be made into a new class of low-density, high-strength mechanical metamaterials and provided insight into the mechanical stability of nanoscale MOFs for practical applications.

Metal–Organic Frameworks and Their Composites for Environmental Applications

“…MOFs, or more generally porous coordination polymers, have been well known as a novel type of porous materials, but it was not until 1990s that this field received great attention, especially because of the pioneering work of Kitagawa and coworkers, [68,69] Yaghi and co-workers, [70,71] and Férey, who first determined the full potential of this ordered solid family. It is a remarkable fact that MOFs have unique porous structure, ordered porosity, rapid mass transfer efficiency, [72] high mechanical strength, [73,74] good antibacterial characteristic, [75] strong degradation ability, [76,77] excellent adsorption performance, [78,79] and strong catalytic performance. [79,80] Due to these superior properties, [81] MOFs have become an ideal and potential material for a variety of sustainable technologies and applications in the last decade, such as chemical sensing, drug transportation, catalysis, gas separation and storage, and water treatment.…”

Structural identification of multidimensional metal–organic frameworks using soft x‐ray tomography

“…In the report of Xing et al, MOF materials with giant pores (290–600 nm) and excellent mechanical strength were successfully synthesized. [ 16 ] The results show that the yield strength and Young's modulus of hierarchical porous framework materials have a property of size dependence, where smaller particles yield stronger and harder properties. The maximum yield strength and Young's modulus reach 580 ± 55 MPa and 4.3 ± 0.5 GPa, respectively, where the specific strength is measured from 0.15 ± 0.03 to 0.68 ± 0.11 GPa•cm 3 /g.…”

Nano‐Metamaterial: A State‐of‐the‐Art Material for Magnetic Resonance Imaging

“…[ 5 ] Subsequently, such a deceptively simple but extraordinarily powerful concept was rapidly extended to a much broader range in the field of electromagnetism, optics, acoustic, and mechanics, and displayed highly distinctive properties, such as ultrahigh positive refractive index, [ 6 ] enhanced nonlinear optical properties, [ 7 ] as well as reprogrammable mechanical stiffness. [ 8,9 ]…”

“…[5] Subsequently, such a deceptively simple but extraordinarily powerful concept was rapidly extended to a much broader range in the field of electromagnetism, optics, acoustic, and mechanics, and displayed highly distinctive properties, such as ultrahigh positive refractive index, [6] enhanced nonlinear optical properties, [7] as well as reprogrammable mechanical stiffness. [8,9] Despite significant advances in the fundamental research of metamaterials, their practical applications in certain fields are still hampered by the limitations of size tailoring, especially in the nanomedicine field where the maximum size is required to be tens to hundreds of nanometers. [10] It has been demonstrated that metamaterials can be manufactured down to the nanometer level (Figure 1b), [11] which shows great promise to expand their potential applications, particularly in the biomedical field.…”