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Abstract

Water stress is a vital security challenge that our world faces, and it is intricately connected to the global energy problem. Scientists and engineers have designed different methods for efficiently purifying water. Among these technologies, membranes in particular have proven to be effective for water purification with decades of productive use. Membrane processes have distinct advantages, including high water quality with easy maintenance, stationary parts with compact modular construction, and excellent separation efficiency. With recent innovations in both analytical and fabrication tools, more advanced membrane technologies are surfacing for a multitude of water purification applications. In this dissertation, we aim to build advanced functional materials for three different membrane systems to manipulate their interfaces to induce selective transport and to apply them for practical use. We have made fundamental insights into the water-membrane interface properties for selective ion transport, yielding first reports of advanced functional materials for several applications. This work begins with fabricating porphyrin covalent organic frameworks (POFs) using a simple one-pot method to modify membranes for solar steam generation. The state-of-the-art applications of covalent organic frameworks for water treatment include desalination, dye removal, and ion capture. We firstly design and fabricate this material for distillation. We demonstrated a universal, simple, and scalable interface engineering strategy for the fabrication of a solar steam generator based on this POF material. Wood@POF, using wood as the template, exhibited about 80% overall process efficiency for solar steam generation under 1.6 Suns illumination. In the next chapter, we demonstrate a route to tune the ion-transport properties of vermiculite membranes by introduction of alkanediamine molecules to crosslink the layers. We show that the interlayer spacing can be tuned by introducing diamines of different molecular lengths, and the crosslinked vermiculite membranes exhibit distinct ion-separation performance. The methodology outlined here could be extended to other layered materials with different inherent layer spacings and electrostatic properties, opening a pathway for designing a diverse range of 2D membrane materials with tunable ion transport. Next, a systematic study of surface charge properties of atomic layered deposition (ALD) grown films in aqueous environments is established. 17 different ALD-grown metal oxide films are synthesized, and a comprehensive study of their water stability, wetting properties, and surface charge properties are provided. This analysis represents a resource guide for researchers, and ultimately for materials and process engineers, seeking to tailor interfacial charge properties of membranes and other porous water treatment components. Lastly, ongoing experimental work in the development of a Janus membrane via ALD is detailed. Detailed characterization of the structure, properties, and function of these membranes will ultimately provide a thorough understanding of ionic transport properties, with ramifications extending beyond the applications explored herein.

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