A New Zirconium Inorganic Building Brick Forming Metal Organic Frameworks with Exceptional Stability

Abstract

Porous crystals are strategic materials with industrial applications within petrochemistry, catalysis, gas storage, and selective separation. Their unique properties are based on the molecular-scale porous character. However, a principal limitation of zeolites and similar oxide-based materials is the relatively small size of the pores, typically in the range of medium-sized molecules, limiting their use in pharmaceutical and fine chemical applications. Metal organic frameworks (MOFs) provided a breakthrough in this respect. New MOFs appear at a high and an increasing pace, but the appearances of new, stable inorganic building bricks are rare. Here we present a new zirconium-based inorganic building brick that allows the synthesis of very high surface area MOFs with unprecedented stability. The high stability is based on the combination of strong Zr−O bonds and the ability of the inner Zr₆-cluster to rearrange reversibly upon removal or addition of μ₃-OH groups, without any changes in the connecting carboxylates. The weak thermal, chemical, and mechanical stability of most MOFs is probably the most important property that limits their use in large scale industrial applications. The Zr−MOFs presented in this work have the toughness needed for industrial applications; decomposition temperature above 500 °C and resistance to most chemicals, and they remain crystalline even after exposure to 10 tons/cm² of external pressure.