This project aims to create porous membranes having sub-nanometer (< 1 nm) sized pores that are aligned along the same direction, have a uniform diameter, and pack in unprecedentedly high pore densities. In this project, one series of ring-like molecules will be prepared in larger (multi-gram) quantities. These cyclic molecules have been found to strongly stack into tube-like structures containing long inner pores. A major objective will be to realize the parallel packing of the corresponding tube-like structures into large-area or membranes. Such a membrane, which contains sub-nanometer pores of a uniform diameters and unprecedentedly high pore density, may offer the next-generation nanoporous materials. These membranes, with their extremely densely packed pores of sub-nanomer sizes, will then be employed to address to a major challenges in separation science: the separation of water molecules from most other ions. If successful, this research may provide a new technology for the desalination of sea water and the purification of polluted water, resulting in major social, economical, and environmental impacts.
The overall goal of this work is to fabricate large-area membranes by homeotropically aligning nanotubular assemblies, and to realize practically useful separation of molecules and ions using such membranes. The central hypothesis is that nantoubular assemblies of rigid macrocycles tend to pack parallel and can be aligned into bulk materials. The rationale for this research is that, once the factors responsible for the alignment of tubular assemblies are elucidated, precise control of the structure of nanopores - which is made possible by synthetically modifying rigid macrocycles will enable the revelation of novel mass-transporting properties of sub-nm pores packed in the bulk phase. The PI proposes to test the central hypothesis by pursuing three specific aims: (1) To design, synthesize and assemble one class of macrocyclic building blocks having an aromatic, tetraurea backbone and an inner cavity of ~5Ã… across; (2) to fabricate membranes consisting of homeotropically aligned arrays of hydrophilic sub-nm pores; (3) to start to explore the rejection of most ions from aqueous solution using the fabricated membranes.
The team proposes to build a focused and sustainable outreach program by developing lecture materials and demonstrations on the science of organic nanopores and their higher assemblies, which will be used by the PI and his graduate students to participate in an existing outreach program in the Buffalo area that spans grades kindergarten through the 12th in local school districts.
