Unravelling surface and interfacial structures of a metal–organic framework by transmission electron microscopy

Zhu, Yihan; Ciston, Jim; Zheng, Bin; Miao, Xiaohe; Czarnik, Cory; Pan, Yichang; Sougrat, Rachid; Lai, Zhiping; Hsiung, Chia-En; Yao, Kexin; Pinnau, Ingo; Pan, Ming; Han, Yu

doi:10.1038/nmat4852

Cited by 344 publications

(369 citation statements)

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“…As can be seen in membranes and photonic crystals [12,13], MOF nanocrystals may merge to form seamless microscopic blocks under mild conditions [14][15][16]. Nevertheless, macroscopic and optical transparent blocks of MOF nanocrystals/microcrystals are still unknown so far.…”

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confidence: 99%

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Room-temperature sintered metal-organic framework nanocrystals: A new type of optical ceramics

Zhou

Wang

et al. 2018

Sci. China Mater.

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Ceramic is a rigid material consisting of an infinite threedimensional network of sintered non-oriented inorganic, non-metallic crystalline grains, which are generally nontransparent. If the inner light scatter is eliminated, ceramics can become transparent or optical ceramics [1,2]. With great potentials in optical windows, sensors and lasers, optical ceramics have received great attentions since 1950s [1]. As the gain medium of solid-state lasers, optical ceramics can combine the advantages of large size, high transparency, high mechanical and thermal stabilities, and ease for dispersing the luminous atoms and groups [3]. For comparison, single-crystal gain mediums can suffer high power density but are difficult to grow into large size, while glasses and polymers have reversed characteristics.To make ceramics transparent, the inner pore and impurity should be minimized to zero, which requires highly pure, nanosized, and very uniform crystallite precursors as well as complicated fusing technology ( Fig. 1) [4,5]. The cubic crystal symmetries (absence of the birefringence which causes extremely high scattering losses) are generally required for the crystallites of optical ceramics, meaning that only a few inorganic materials can be used. Besides, ceramics sintering usually operates above 1000 o C, which excludes organic and organic-inorganic hybrid materials [1].Porous coordination polymers (PCPs) or metal-organic frameworks (MOFs) are crystalline materials consisting of metal ions and organic ligands, which have captured widespread attentions for adsorption, catalysis, sensing, optics [6] and also laser gain mediums [7][8][9][10][11]. As can be seen in membranes and photonic crystals [12,13], MOF nanocrystals may merge to form seamless microscopic blocks under mild conditions [14][15][16]. Nevertheless, macroscopic and optical transparent blocks of MOF nanocrystals/microcrystals are still unknown so far. Just like single crystals and optical ceramics, increasing the block size with high optical quality is always a great challenge for many materials. Here, we show that by simply slowing down the solvent evaporation rate, nanocrystals of the prototypical MOF SOD-[Zn(mim) 2 ] (MAF-4/ZIF-8 [17,18], Hmim = 2-methylimidazole, Fig. 2) with the cubic crystal symmetry can fuse at room temperature to form large transparent blocks. After doping laser dye, this metal-organic optical ceramic (MOOC) can show the amplified spontaneous emission (ASE) with a very low energy-density threshold.MAF-4 nanocrystals with uniform size (ca. 20 nm) can be easily synthesized by reaction of Zn(NO 3 ) 2 and Hmim in methanol or ethanol at room temperature (Fig. S1). Compared with the commonly used solvent methanol [19], ethanol is nontoxic and more environment-friendly. After centrifugation and washed, the residual nanocrystals and solvent form a white gel-like (semi-fluidic) block.

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confidence: 99%

“…S6). The close contacts between MOF nanoparticles have been rarely studied [14][15][16]. It is well known that crystals in solvent are not static but actually undergoing recrystallization.…”

mentioning

confidence: 99%

Room-temperature sintered metal-organic framework nanocrystals: A new type of optical ceramics

Zhou

Wang

et al. 2018

Sci. China Mater.

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“…The fast development of electron microscopy has enabled unprecedented achievements in the field of life science and materials science [1][2][3][4][5][6]. In particular, the 2017 Nobel Prize of chemistry was awarded to three scientists who contributed significantly to developing cryo-electron microscopy (Cryo-EM) [7].…”

Section: Yong Wangmentioning

confidence: 99%

“…To minimize the effect of electron beam irradiation, materials scientists usually lower the operating voltage or electron dose during the TEM experiments [8]. Recently, Zhu et al successfully acquired the atomic structure of a MOF with the help of direct-detection electron-counting camera (Gatan K2 Summit) [6]. However, if materials are also sensitive to ambient conditions, like lithium, which is extremely prone to oxidation, how to address this challenge and secure the atomic structure of intrinsic lithium by TEM?…”

Section: Yong Wangmentioning

confidence: 99%

“…(2) are the observed structures and chemical distribution identical as those in dynamic operating conditions? Alternatively, one may utilize inert gases to protect the environment-sensitive materials (such as using gas cell system in TEM [12,13]) and marry with advanced imaging system (such as Gatan K2 camera [6]) to obtain atomic-scale information of environment-sensitive materials.…”

Section: Yong Wangmentioning

confidence: 99%

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