This one-year EAGER award addresses the early stage fabrication of nanoporous membranes containing non-deformable pores with a uniform, subnanometer size. The resultant membranes will be used for water purification and desalination, as well as other size- and property-dependent molecular separations.
The primary focus will be the use of a highly efficient, one-pot synthetic method for preparing large amount of macrocyclic building blocks that will then be used for engineering the membranes. The building blocks are macrocycles sharing a rigidified, cyclic backbone that contain a non-collapsible hydrophilic cavity of ~5-6 angstroms. Recent studies indicate that this class of macrocycles have a high propensity to associate into 1D tubular assemblies. Based on preliminary results, analogous macrocycles with side chains carrying polar terminal groups should self-assemble into nanoporous membranes. The alignment of the 1D tubular assemblies in the capillary pores of anodic alumina membranes will be probed. Computer simulation will be performed to investigate transport (nanofluidic) behavior of water within the nanopore under different external pressures and to evaluate the permeability of the membrane to various ionic species in a solvent as a function of size of nanopores. Optimally designed membranes are expected to reject most small molecules and ions and will be assessed as nanofiltration membranes for water desalination.
The proposed research is highly interdisciplinary. Graduate and undergraduate students of various backgrounds will gain skills in multiple fields involving chemistry, materials science and the engineering of corresponding molecules and devices. Specifically, the educational impacts of this joint research include: (1) The unique opportunity to combine computer-aided design, synthesis, and characterization of molecular, supramolecular, and nanosized structures with the engineering of the corresponding materials and devices in the training of graduate students. (2) The program will involve undergraduate students, particularly those from groups traditionally underrepresented in sciences and students, who have limited exposure and access to the latest developments in the corresponding fields. (3) The research results will not only be published in highly visible journals to broadly disseminate this work to scientific society at large, but more importantly, will lead to many practical applications. Insights obtained from the construction of nanosized building blocks and the assessment of their 1D assembly will in turn will help the development of concepts generally useful for addressing other problems in the field of chemical and biological separation.
This one-year EAGER grant supports the initial stage of our long-term effort in creating molecular and supramolecular structures that contain various nano- and subnanometer with uniform pore sizes. The specific objective of this project is to establish efficient method for preparing cyclic molecules called macrocycles. These donut-shaped molecules contain internal cavities of unchangeable (rigid) but tunable sizes. They are designed as the basic building blocks for forming tube-like structures call self-assembling (means automatic formation without external influence) nanotubes that contain internal lumen of fixed diameter. Numerous results based on basic studies show that nanopores, especially pores with subnanometer (<1 nanometer) diameters, have abilities to allow molecules or ions to pass in highly selective and efficient ways. We have established methods for preparing four major types of such molecular donuts using readily available, economic materials in very high overall yields. The high efficiency of our method allows the manufacturing of these molecular building blocks in large (industrial) scale, which has paved the way for preparing nanoporous membrane with very high pore densities and uniform pore sizes. The eventual availability of these next-generation porous materials will lead to major progress in separation science, especially in areas that unmet challenges such as the efficient separation of drug molecules, the removal of pollutants from environment, and the purification of water at affordable expenses.
