Investigating the role of defects in adsorption mechanisms of metal-organic frameworks and fabrication of crystal-glass composites

Optimized adsorbents could greatly contribute to lowering the carbon footprint and energy consumption in the industrial separation processes and in domestic heating and cooling, which currently account for up to 40 % of total global energy consumption. Among all the known adsorbents, metal-organic frameworks (MOFs) are the most flexible and suitable materials that have the potential to be widely used in this regard. The wide-ranging properties of MOFs rely in many cases on the presence of defects within their structures and the disorder that is inevitably associated with such defects. However, identifying the type and location of defects in MOF structures and tuning their amounts and distribution for further improvements are still great challenges. In the research project, we will undertake a systematic study of inherent and deliberately-created defects in zeolitic imidazolate frameworks (ZIFs), a promising subfamily of MOFs that resembles the structures of inorganic zeolites. The impact of defects on adsorption properties with a focus on the adsorption of small alcohol molecules will be evaluated. The understanding of the alcohol adsorption mechanisms is particularly important for further optimizations of the materials for their efficient use in the adsorption-based biofuel purification processes and for improving their performances in the low-temperature heat reallocation systems, where water cannot be used as a working fluid (low freezing point, slow diffusion). The structural characterization will be obtained by the advanced solid-state NMR (SSNMR) methods and a few new approaches will be developed to tackle the defects in ZIFs and the host-guest interactions during the adsorption. Very recently, ZIFs were recognized as the fourth type of melt-quenched glasses, the first among them to have a permanent microporosity accessible to gases, without any post-synthetic treatments. This opened a new possibility of shaping these functional materials in glass monoliths and crystal-glass composites. In the last part of the project, the best performing ZIFs will be fabricated into glasses and crystal-glass composites. With SSNMR we will examine the interactions between crystalline and glassy nanodomains and compare their adsorption properties to their pristine counterparts.