Tunable and ordered porous carbons with folding-like nanoscale framework via interdigitation and twisting

Abstract

Nanoscale folded structures, such as protein folds, extensively exist in nature and are key to controlling various physicochemical functions; however, their controlled expressions in both organic and inorganic solid matter are still limited. In this paper, the sugar (D- and L-fructose)-derived, hydrothermal synthesis of ordered porous carbonaceous materials with a long-range, folded nanoscale framework is reported. The block copolymer-templated carbonaceous precipitates demonstrate the presence of twisted lamellae-like ordered nanostructural motifs with a repeating distance of ca. 20 nm, as revealed via detailed electron microscopy studies. Furthermore, the synchrotron X-ray scattering study unravels a threefold symmetry, indicating the nanostructural configuration, where the formed mutually nearly identical layering modes are related by a threefold axis and further interpenetrate each other. Owing to this interpenetration, the developed carbonaceous framework is interdigitated on the nanoscale, while the accompanying twisting event folds (i.e., integrates) the system. The proposed mechanism is based on the interplay of the chemical condensation of sugar (i.e., a chiral carbon precursor) and its binding to polymer template inducing layered dimensional ordering. Template removal yields porous carbonaceous bodies with folded lamellae-like ordering modes interpenetrating each other and, therefore, being stabilized, and with the knot-like motif observed locally, due to the complex interdigitation. The extended process controllability of the hydrothermal carbonization allows pore size control by varying the composition of the starting solution. The presented novel porous carbonaceous frameworks would provide large surface area porous bodies with added functions, such as increased intactness (i.e., stability) of the framework, chiral selectivity, or potentially mechanical flexibility, providing interesting features that can be studied for future advancements in electrochemistry and separation and catalysis sciences.