Transparent and High-porosity Aluminum Alkoxide Network-forming Glasses

Abstract Metal-organic network-forming glasses are an emerging type of material capable of combining the modular design and high porosity of metal-organic frameworks and the high processability and optical transparency of glasses. However, a generalizable strategy for achieving both high porosity and high glass forming ability in modularly designed metal-organic networks has yet to be developed. Herein, we developed a new series of metal-organic network-forming glasses, aluminum alkoxide glasses, by linking aluminum-oxo clusters with alcohol linkers in the presence of a modulator template. These glasses exhibit well-defined glass transitions and high surface areas up to 500 m2/g, making them one of the most porous glassy materials. The aluminum alkoxide glasses also have optical transparency and fluorescent properties, and their structures were elucidated by pair-distribution functions and compositional analysis. A systematic glass transition study suggested that progressive increase in network connectivity during the evaporation of a coordinatively competitive solvent is key to the bottom-up glass synthesis. Aluminum alkoxide glass can also encapsulate crystalline MOFs to yield composite materials with higher porosities. These findings could significantly expand the library of microporous metal-organic network-forming glasses and enable their future applications.