U.S.-Ireland R&D Partnership: AQUASORB: Predictive Modeling of Atmospheric Water Sorption

North Carolina State University, Raleigh NC

Investigators

Abstract

NON-TECHNICAL SUMMARY The Division of Materials Research and the Division of Chemical, Bioengineering, Environmental and Transport Systems contribute funds to this award, which supports the AQUASORB research team taking an innovative approach to the discovery and development of materials for capturing water. The PIs include the Space group at North Carolina State University, the Zaworotko group in Ireland and the James group in Northern Ireland. The tripartite team seeks to produce superior water sorption materials to address a variety of pressing national and world needs. For example, access to fresh water typically occurs from sources such as lakes, rivers, precipitation, glaciers and groundwater. Unfortunately, conventional water sources are unevenly distributed and, according to the United Nations, by 2025, two out of three people worldwide will be living in a territory facing a freshwater crisis. Thus, atmospheric water harvesting and dehumidification are the focus problems. Whereas only 0.04% of water exists as atmospheric water, this represents a vast quantity (about 1.29 x 10^16 liters!) and is infinitely renewable. Further, humidity control is critically important for industries such as food production, pharmaceuticals, chemical processing and petroleum refining. Current technologies for dehumidification are energy intensive, using as much as 50% of the energy footprint of air handling systems and consuming 5-10% of global energy production. Driven by insights provided by modeling, the Space group will lead the team to produce transformative materials with our experimental partners to address the need for plentiful fresh, water that is renewable, widely available and inexpensive. Specifically, the activities focus on materials discovery and design via an iterative cooperative approach. The project leverages synergy between an international team to study experimental sorption performance in hybrid ultramicroporous materials (Zaworotko, Ireland) and porous liquids (James, N. Ireland) to enable the development of predictive models (Space, USA) for sorbent performance. The diverse project will provide educational training spanning theoretical modeling, materials synthesis and the design of systems for practical water harvesting. Students will interact across disciplines and locations developing a powerful skill set for future impactful work in the age of tailor-made materials for grand challenge problems. The aim is to produce and employ modeling that will usefully guide synthetic materials chemists, using the power of high quality, reliable molecular modeling. Simulations, synthesis and materials evaluation are needed to jointly address sorbent material performance under different conditions. Rational insights will be sought into controlling, harvesting and manipulating water in porous materials via our experimental / theoretical team, supporting human flourishing on a global scale. TECHNICAL SUMMARY The Division of Materials Research and the Division of Chemical, Bioengineering, Environmental and Transport Systems contribute funds to this award, which supports the AQUASORB research team taking an innovative approach to the discovery and development of materials for capturing water. The PIs include the Space group at North Carolina State University, the Zaworotko group in Ireland and the James group in Northern Ireland. The development of energy efficient approaches for water harvesting is a global challenge because of its critical relevance to three key sectors: atmospheric water harvesting, dehumidification and farming. The Problem to be Addressed by AQUASORB: Whereas solid desiccants enable several current technologies for water capture, they suffer from two major drawbacks: (i) High energy footprint: Water capture is not in itself a challenge as there are many inexpensive desiccants that readily capture water, even at low relative humidity. The subsequent release of water is a different matter. This is because most effective commercial sorbents work too well; their regeneration generally requires heating at high temperatures, well above the boiling point of water. (ii) Poor performance at low relative humidity: The most widely used commercially available desiccants such as commercial silica, have a relatively low (but still high) energy footprint and tend to perform much less effectively at low humidity. Despite finding utility in commercial dehumidification applications, such desiccants are unsuited for water harvesting applications where most needed, i.e arid regions. These factors render the current generation of desiccants commercially unsuitable or expensive for water harvesting because of their high energy costs and the resulting high carbon footprints. The solution: AQUASORB – a Tripartite Medley of Modeling and Experiment – A Virtuous Cycle of Materials Discovery. The team will take an innovative approach to the discovery and development of the next generation of regeneration optimized desiccants. Given the context above, it is unsurprising that there is high interest in the development of new energy efficient liquid and solid desiccants. Currently, the number of reported desiccants in these respective fields is enormous, and growing. In essence, the number of potential desiccants is growing exponentially but the experimental screening of these desiccants is time‐consuming and expensive. AQUASORB will address this challenge by exploiting the expertise of the groups of Zaworotko (University of Limerick, desiccant synthesis, and characterization), James (Queen’s University Belfast, porous liquid application of desiccants) and Space (North Carolina State University, materials modeling and design) to develop a predictive approach to identify new desiccants with regeneration optimized capture/release performance. These desiccants will capture and release atmospheric water with high working capacity, low energy of desorption and fast kinetics by having just the right level of water binding – not too strong and not too weak. AQUASORB’s ultimate objective is two-fold: (i) to advance the science of water sorption modeling in order to (ii) identify desiccants that capture water vapor under ambient conditions and release that water with a low energy footprint. Meeting these requirements will enable disruptive new water harvesting technologies. The Space group leads in modeling interfaces and porous materials with a track record of innovation over two decades and will lead the team via materials modeling and design. The project leverages expertise in simulations, evolved through productive working relationships with our experimental partners, to tackle water sorption materials. This includes the substantial challenge of adding water to our force field such that its behavior in a variety of porous solids is reliably described. We have expanded our extensive collaboration on porous materials with the Zaworotko Group at the University of Limerick to include porous liquids with the James group at Queens University Belfast seeking to understand water in complex materials that will lead to practical solutions for people. Insights to control the subtle balance between water sorption energetics and entropics when ordered within a structure will be pursued. Accurately capturing water structure in complex environments and abstracting its essential behavior is a master challenge ideally suited to the strengths of our productive experimental / theoretical AQUASORB partnership. The resulting force field and modeling innovations will be shared with the scientific community including making our codes widely available while incorporating them into commonly used programs. Iterative team materials design and evaluation will be pursued with experimental synthesis and characterization fueled by advanced modeling. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.