Principles of Chemical Recognition and Transport in Extractive Separations
This provides new understanding of the theoretical, synthetic, structural, and thermodynamic principles of molecular recognition leading to unprecedented selectivity and control of ion binding in separations such as liquid-liquid extraction and crystallization. The major line of inquiry deals with the design of fully functional ion receptors that can completely accommodate the coordination and charge-neutralization requirements for separation of ions, ion pairs, or ion aggregates, whether the recognition occurs with discrete molecular receptors or small molecular units that function by self-assembly. Three specific aims deal with computer-aided molecular design to guide the discovery of molecular structures with controlled functionality; self-assembly of small molecular units with multiple ions to form predetermined structures; and cooperativity effects in the selective separation of ions and ion pairs. Specific progress is being made with new anion-binding motifs based on new guanidinium, urea, and calixpyrrole platforms, and when these are combined with cation-binding groups, the resulting ditopic structures self-assemble with ion-pairs in high-order assemblies. Resulting transformative understanding of the theoretical, structural, and thermodynamic principles underlying ion recognition will strongly benefit DOE’s energy, environmental, and national-security missions.