Ultralight and mechanically robust carbon monoliths with aligned microchannels

While macroporous carbon materials have attracted considerable attention due to their tunable porosity, chemical and thermal stability, and electrical conductivity, they still face critical limitations in achieving a balance of ultralow density, high mechanical toughness, and efficient fluid transport through a cost-effective and environmentally friendly approach. To address these issues, an ice-templating approach is employed to fabricate ultralight yet mechanically robust carbon monoliths with aligned microchannels. By unidirectionally freezing a precursor suspension containing cellulose nanofibers and a carbon source, followed by freeze-drying and pyrolysis at 900 °C, we obtain honeycomb-like structured carbon monoliths with an ultralow density (∼0.09 g cm^-3), a high compressive strength (∼3400 kPa), and well-penetrated microchannels for efficient mass transport with minimal pressure drop. The potential of these materials is demonstrated in two key applications: high-flux water purification, achieving >99% removal of rhodamine B at an exceptional flux of 20 000 L m^-2 h^-1 with excellent reusability, and rapid heat exchange of flowing water, exhibiting a heat exchange efficiency four times greater than that of commercial counterparts. This study offers a versatile strategy for designing ultralight, mechanically robust, and highly permeable macroporous carbon materials with promising applications in environmental and energy-related technologies.