Controlled fabrication of orchid-like nitrogen-doped hierarchical porous carbon and hollow carbon nanospheres

Flower-like porous carbon has fascinated significant attention due to its outstanding and exceptional properties. However, controlled synthesis of porous carbon with adjustable morphology, highly active sites and cross-linked pore channels remains still a great challenge. Herein, an inimitable dissolution–reassembly anisotropic growth strategy was firstly demonstrated for the fabrication of idiographic orchid-like hierarchical porous carbon with ultra-thin multilayer carbon sheets, high specific surface area (1063 m² g⁻¹), large pore volume (0.82 cm³ g⁻¹) and rich nitrogen content (7.6 wt%). Highly reactive phloroglucinol and EDA aggregated magically and SiO₂ acted as a pore former. Ingeniously, acetone acted as a “surgical knife,” which cut the composite of SiO₂@phloroglucinol–EDA into many tiny units and further anisotropic growth into orchid-like polymers. The width and thickness of the carbon petals can be effectively controlled with the diversification of acetone concentration. Intriguingly, monodisperse hollow carbon nanospheres could be harvested with silicon-deficient system, which may offer new insight into the construction of functionalized carbon materials with hollow architecture. Owing to the unmatched superstructures, orchid-like carbon materials can be employed as an ideal drug carrier and dye adsorbent.

Figure Schematic illustration of solid carbon nanosphere, hollow carbon nanosphere and OHPC-25. For the first time, a novel dissolution–reassembly route based on strong hydrogen-bonding interaction was developed to prepare unique orchid-like hierarchical porous carbon, in which phloroglucinol acted as a carbon precursor and EDA both as a base catalyst and as a nitrogen precursor. The critical step to this synthetic approach was the ingeniously employed acetone as a “surgical knife” to cut the composite of SiO2@phloroglucinol–EDA into many tiny units, and these units were reassembled into orchid-like polymers. After adding acetone, the morphology of carbon materials has changed from solid nanospheres to hollow nanospheres. This strategy did not use any template as the cavity, which may offer a new insight into the comprehension of synthesized functionalized carbon materials with hollow architecture.