Our goal

Address challenges in critical materials separation

The overarching goal of this research is to address the urgent need for sustainable recovery of critical materials—elements essential to advanced electronics and chip manufacturing. Central to the research program lies the challenge of rethinking the canonical design principles of extractants used in metallurgical processes. This effort stems from the poor selectivity of metal extractants when separating neighboring elements, particularly in complex substrates such as modern e-waste. Most extractants used in e-waste recycling target metal cations while overlooking the role of counter anions. In material leachates, high concentrations of anions (e.g., chloride, nitrate) often associate with metal ions, affecting their apparent stability (Figure 1a). Meanwhile, complexation within confined spaces can generate unique coordination modes with unrecognized potential for separations (Figure 1b). We believe that receptors exploiting these anion-metal interactions and spatially constrained complexation will enhance selectivity in separations and reduce secondary waste generation. The targeted elements include Li, Mn, Co, Ni, and the lanthanides (Ln).

Figure 1. Overview of projects in the DH-lab: (a) complex speciation and counter anions, (b) complexation in confined spaces, and (c) separation under external stimuli. (charge omitted).

Additionally, we aim to explore novel mechanisms for achieving catch-and-release of critical materials. For quite some time, complexation and decomplexation of bound ions have relied on pH modulation. While effective in some cases, this approach constrains receptor design to ionic or amine-based scaffolds and often fails to deliver sufficient selectivity among chemically similar elements. Alternatives are needed. Stimuli-responsive receptors offer an attractive solution by enabling distinct coordination modes in response to external stimuli, thereby facilitating the catch-and-release of target ions (Figure 1c). We believe that judiciously designed receptors of this kind will expand the toolbox of extractants available to separation science.

On this basis, three projects are proposed and outlined as follows:

I applaud your patience if you have made it thus far! Interested students are encouraged to get in touch with Dr. Huang.