Porous Polymers for Water Purification and Electrical Energy Storage
Porous polymers contain empty spaces that facilitate valuable functions, including host-guest chemistry and enabling ion transport. For example, insoluble polymers of β-cyclodextrin (β-CD), an inexpensive, sustainably produced macrocycle of glucose, are of interest to remove micropollutants from water by means of adsorption. Previous cross- linked β-CD polymers have low surface areas and poor adsorbent performance compared to conventional activated carbons (ACs). Our high surface area β-CD polymer rapidly sequesters organic micropollutants with adsorption rate constants 15-200 times greater than ACs and nonporous β CD adsorbents and the outperformed a leading AC for the instant removal of a complex mixture of organic micropollutants at environmentally relevant concentrations.
Periodic porous polymers known as covalent organic frameworks (COFs) provide designed control over porosity and can also predictably organize redox-active groups. The limited chemical and oxidative stability of established COF linkages, such as boroxines and boronate esters, precludes these applications, and the electrochemical characterization of 2D COFs are only now appearing. I will present a β-ketoenamine-linked 2D COF that exhibits reversible electrochemical processes of its anthraquinone subunits, excellent chemical stability to a strongly acidic electrolyte, and one of the highest surface areas of the imine- or enamine-linked 2D COFs. Electrodes modified with the redox-active COF show higher capacitance than those modified with a similar non-redox-active COF, even after 5000 charge-discharge cycles. Thin films of these materials show nearly quantitative electrochemical addressability of their anthraquinone subunits. These findings demonstrate the promise of using 2D COFs for capacitive storage.