Growth of Metal–Organic Framework within Macroporous PEDOT:PSS Aerogels Prepared by Directional Freezing for Supercapacitors

Supercapacitors have gained popularity as a technology widely used in energy storage and industrial applications due to their high power density and ability to charge and discharge rapidly. In particular, metal–organic frameworks (MOFs), nanoporous materials constructed from metal-based nodes and organic linkers, have been explored for energy storage because of their high porosity and surface area. However, further advances in supercapacitors by MOFs are limited because most MOFs are electrically insulating and chemically unstable in aqueous electrolytes. This work integrates porous conductive polymer scaffolds and MOFs to overcome the challenges of MOFs-based materials in supercapacitors. First, we employed directional freezing to an aqueous solution of conductive polymer, poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). This strategy led to macroporous PEDOT:PSS aerogels, which allow the further growth of a water-stable zirconium-based MOF, UiO-66. Redox-active manganese sites were then immobilized on the defective sites of UiO-66 to render the redox-hopping charge conduction within the framework. The resulting Mn-UiO-66/PEDOT:PSS composite aerogels are employed as active materials for supercapacitors with remarkable power density and rapid charge–discharge capabilities. When compared to the conventional random freezing method without a controlled temperature gradient, directional freezing provided more uniform PEDOT:PSS macropores and scaffolds to facilitate the growth of UiO-66, leading to enhanced electrochemical performance. Furthermore, the initial PEDOT:PSS aqueous solution exhibited suitable rheological behavior for extrusion-based 3D printing to shape MOF-based composites. In summary, we provide a simple strategy to prepare functional composites by UiO-66 and conductive aerogels for high-performance supercapacitors.