We have discovered and clarified the ultrahigh glass-forming ability of the metal-organic frameworks—ZIF-62 [Zn(Im _{2− x} bIm _x )].

Glassy metal-organic frameworks: The node-and-linker structure of metal-organic frameworks could enable detailed structural studies of molecular glasses quenched from melts. Zinc-based zeolitic imidazole frameworks exhibit a high propensity for glass formation at conventional cooling rates. Madsen et al. used ultrahigh magnetic fields (19.5 and 35.2 tesla) to perform zinc-67 nuclear magnetic resonance of solid samples with magic-angle spinning on three samples with different ratios of imidazole and benzimidazole linkers. The structural disorder of the tetrahedral ligand environment around zinc nodes was higher in the glassy states than in the parent crystals. Science , this issue p. 1473

To date, only several microporous, and even fewer nanoporous, glasses have been produced, always via post synthesis acid treatment of phase separated dense materials, e.g. Vycor glass. In contrast, high internal surface areas are readily achieved in crystalline materials, such as metal-organic frameworks (MOFs). It has recently been discovered that a new family of melt quenched glasses can be produced from MOFs, though they have thus far lacked the accessible and intrinsic porosity of their crystalline precursors. Here, we report the first glasses that are permanently and reversibly porous toward incoming gases, without post-synthetic treatment. We characterize the structure of these glasses using a range of experimental techniques, and demonstrate pores in the range of 4 – 8 Å. The discovery of MOF glasses with permanent accessible porosity reveals a new category of porous glass materials that are elevated beyond conventional inorganic and organic porous glasses by their diversity and tunability.

Metal–organic framework (MOF) glasses are characterized by the possession of both inorganic and organic components, linked in a continuous network structure by coordination bonds. To the best of our knowledge, the optical properties of MOF glasses have not been reported until now. In this work, we prepared a transparent bubble-free bulk MOF glass, namely, the ZIF-62 glass (${\mathrm{ZnIm}}_{2-x}{\mathrm{bIm}}_x$), using our newly developed hot-pressing technique, and measured its optical properties. The ZIF-62 glass has a high transmittance (up to 90%) in the visible and near-infrared wavelength ranges, which is comparable to that of many oxide glasses. Using the Becke line $n_D$ method, we found that the ZIF-62 glass exhibits a refractive index (1.56) similar to most inorganic glasses, though a lower Abbe number ($\sim 31$).

The last 20 years have seen many publications investigating porous solids for gas adsorption and separation. The abundance of adsorbent materials (this work identifies 1608 materials for CO₂/N₂ separation alone) provides a challenge to obtaining a comprehensive view of the field, identifying leading design strategies, and selecting materials for process modeling. In 2021, the empirical bound visualization technique was applied, analogous to the Robeson upper bound from membrane science, to alkane/alkene adsorbents. These bound visualizations reveal that adsorbent materials are limited by design trade‐offs between capacity, selectivity, and heat of adsorption. The current work applies the bound visualization to adsorbents for a wider range of gas pairs, including CO₂, N₂, CH₄, H₂, Xe, O₂, and Kr. How this visual tool can identify leading materials and place new material discoveries in the context of the wider field is presented. The most promising current strategies for breaking design trade‐offs are discussed, along with reproducibility of published adsorption literature, and the limitations of bound visualizations. It is hoped that this work inspires new materials that push the bounds of traditional trade‐offs while also considering practical aspects critical to the use of materials on an industrial scale such as cost, stability, and sustainability.

The Ti–O–C interactions between GO and TiO ₂ are strong enough to induce mutual shaping during synthesis and thermal treatment.