Nanoporous Transparent MOF Glasses with Accessible Internal Surface

Abstract

While glassy materials can be made from virtually every class of liquid (metallic, molecular, covalent, and ionic), to date, formation of glasses in which structural units impart porosity on the nanoscopic level remains undeveloped. In view of the well-established porosity of metal-organic frameworks (MOFs) and the flexibility of their design, we have sought to combine their formation principles with the general versatility of glassy materials. Although the preparation of glassy MOFs can be achieved by amorphization of crystalline frameworks, transparent glassy MOFs exhibiting permanent porosity accessible to gases are yet to be reported. Here, we present a generalizable chemical strategy for making such MOF glasses by assembly from viscous solutions of metal node and organic strut and subsequent evaporation of a plasticizer-modulator solvent. This process yields glasses with 300 m(2)/g internal surface area (obtained from N2 adsorption isotherms) and a 2 nm pore-pore separation. On a volumetric basis, this porosity (0.33 cm(3)/cm(3)) is 3 times that of the early MOFs (0.11 cm(3)/cm(3) for MOF-2) and within range of the most porous MOFs known (0.60 cm(3)/cm(3) for MOF-5). We believe the porosity originates from a 3D covalent network as evidenced by the disappearance of the glass transition signature as the solvent is removed and the highly cross-linked nanostructure builds up. Our work represents an important step forward in translating the versatility and porosity of MOFs to glassy materials.

Unraveling the effects of linker substitution on structural, electronic and optical properties of amorphous zeolitic imidazolate frameworks-62 (a-ZIF-62) glasses: a DFT study

“…[1][2][3][4][5][6][7] In addition to these applications of crystalline MOFs, recent research has discovered that melting and then quenching some crystalline MOFs leads to the formation of MOF-glass. [8][9][10][11] Although a huge number of crystalline MOFs exist, the discovered MOF glass derives from few of the MOFs. These MOFs mainly are zeolitic imidazolate frameworks (ZIFs).…”

Amorphous 2D materials containing a conjugated-polymer network

“…Our intention here is to prepare the low-crystalline 2D structures in both lateral and vertical directions to study the exfoliation behavior. Although amorphous states were observed in frameworks and layered materials [26][27][28][29][30][31][32][33] , the amorphous nature was not applied to the exfoliation. A recent report shows that grafting of bulky alkyl chains on the layer of a COF induced smooth exfoliation into the nanosheets 34 .…”

Soft Porous Crystals: Extraordinary Responses to Stimulation

“…70 However, there is a scarcity of works dealing with the impact of this metal center disorder on MOF properties in general, and on flexible frameworks in particular. 74,75, Finally, we note that while there have been many experimental studies of amorphous phases of MOFs 76,77,77,79 (for a brief review, see Ref. ), they are for now unexplored from the computational point of view.…”