H-bonded Open Framework (HOF) materials for Indoor Air Quality: towards simultaneous regulation of H2O and CO2 levels

• Applicant: Professor Dr. Christoph Janiak
• Subject Area: Inorganic Molecular Chemistry - Synthesis and Characterisation
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 545525712

Indoor air quality (IAQ) has a major impact on human health. Many Europeans spend over 90% of their time indoors, and most of the 10,000 liters of air they breathe every day is composed of indoor air. In a closed environment, the concentration of CO2 is higher than that measured outdoors (400 ppm or 0.04%), mainly due to the carbon dioxide exhaled by occupants (the air exhaled by a human being contains between 4000 and 5000 ppm of CO2). An indoor value of 1000 ppm (1800 mg/m3) is generally considered a reference value in many European countries, concentrations in excess of 1000 ppm are likely to cause feelings of discomfort, such as fatigue, loss of concentration or headaches. Relative humidity levels are also an important factor influencing occupant comfort. Too high a humidity level (over 90%) increases the intensity of hot or cold temperatures, while too low a humidity level (below 20%) can lead to irritation of the eyes, nose and throat. Typically, humidity and CO2 are diluted and removed from buildings by air ventilation, but this requires a necessary air-conditioning infrastructure and simply opening a window is not always possible. Also, a desiccant can dehumidify the air in combination with a conventional air-conditioning system to prevent inefficient over-cooling of the air below its dew point. Silica gels and zeolites are often used desiccants but are not very efficient for dehumidification because silica gels have a linear uptake over the whole water partial pressure range and zeolites are too hydrophilic and require a high regeneration temperature. In this proposal, we intend to design microporous H-bonded open frameworks (HOF) materials with H2O and CO2 adsorption characteristics that can autonomously attenuate H2O and CO2 levels, i.e., bring humidity below 60% and CO2 levels below 1000 ppm, and position these materials as potential maintenance-free adsorbents for humidity and CO2 control in confined spaces. The HOFs considered are based on SPA-1 and SPA-2 compounds developed by the group in Toulouse. In collaborative preliminary work we have demonstrated that these HOFs have the possibility of exerting precise control over the chemical functionalization of pores in a given H-bonded structure, without modifying the topology of the reference structure, and thus fine-tuning the sorption characteristics of the material. The synthesis and characterization of these tunable HOFs will be developed with special emphasis on guest-accessible void, structural and chemical stabilities, sorption characteristics and activation conditions for autonomous cyclic water and carbon dioxide sorption. The deposition of these HOFs on solid support materials with binders will be done. Applications for simultaneous H2O and CO2 regulation in indoor air will be investigated.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partner: Dr. Jean-Pascal Sutter