The development of effective phosphate receptors is an important remediation tool to mitigate the damaging environmental effects of phosphate eutrophication. However, our understanding of recognition at the aqueous interface is underexplored, which has hindered the rational design of surface receptors. The unique environment present at the air/water interface has remarkable advantages over recognition in bulk solution. It is also technologically-relevant, as interfaces are prevalent in remediation membranes. In this study, we explored a homologous series of synthetic receptors differing in functional group, charge, and number of alkyl chains to characterize the driving forces of aqueous interfacial recognition. We have found that the functional group at the binding site using guanidinium and thiouronium receptors and organization of the receptors using two alkyl anchoring groups were important design features for phosphate binding. The guanidinium and thiouronium receptors were 1000 and 10 fold more selective for phosphate over chloride respectively, at chloride concentrations mimicking natural waters. Charge screening at high chloride concentrations led to a decrease in the binding affinity due to significant weakening of the electrostatic potential of the receptors. This study helps merge the physical and organic communities in their understanding of receptor design for phosphate remediation and provides some of the first understanding of phosphate recognition at the air/water interface.

Chemical, physical, and superstructural driving forces of aqueous interfacial phosphate recognition

2019 Fall National Meeting

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