Chemistry and Water Harvesting Properties of Covalent Organic Frameworks (COFs)
Covalent organic frameworks (COFs) have emerged as an advanced class of materials that are porous, crystalline, and extended structures. To diversify the chemistry of COFs, more novel COF topologies (i.e., structure types) are needed. Herein, we design the triangular linker that bears a unique conformational structure. We further reticulate it into an unseen COF topology, namely fjh COF, by reacting with square-planar linkers. Additionally, we promote the use of COFs for water harvesting from air. Particularly, we report the synthesis of a 2D COF containing one kind of well-defined pore structure with 8Å and its unique water sorption behavior: steep uptake at low relative humidity (34% RH), low generation temperature, and high water vapor stability. To make COFs that can take up water at even lower RH suitable for capturing water under arid conditions, we further synthesize a series of 2D hydrazine-hydrazide-linked COFs by post-synthetic oxidation of COFs having hydrazine linkages. One of the oxidized COFs exhibits high water capacity and steep-step uptake of water isotherm at 10 to 20% RH. Our strategy of using 2D COFs with optimized pore structures and hydrophilicity provides a forward step in implementing COFs for practical applications in general and water harvesting from air in specific.
Dr. Nguyen obtained his Ph.D. from the University of Technology, Vietnam National University at Ho Chi Minh City (Vietnam) in 2017. He spent almost a year working at King Fahd University of Petroleum and Minerals (Saudi Arabia) as a Research Consultant before joining the group of Prof. Omar Yaghi at the University of California Berkeley where he is currently a Postdoctoral Researcher. Dr. Nguyen was a Visiting Professor at the United Arab Emirates University (United Arab Emirates) in 2021. Dr. Nguyen focuses his research on the design and synthesis of novel reticular materials (metal–organic frameworks and covalent organic frameworks) for water uptake and carbon capture and conversion. He was listed in the top 2% of scientists in his field identified by Stanford University in two successive years 2020 and 2021.