Poplar catkin-derived self-templated synthesis of N-doped hierarchical porous carbon microtubes for effective CO2 capture.

Graphical abstract Highlights • Poplar catkins-derived N-doped hierarchical porous carbon microtubes were obtained. • Our facile approach represents an example of trash-to-treasure transformation. • The porosity, surface structure, tube wall thickness can be tailored. • The optimal porous carbon microtube sample shows a satisfactory CO 2 uptake. • It also exhibits an excellent CO 2 /N 2 adsorption selectivity and recyclability. Abstract Poplar catkins are an environmental pollutant because they can trigger sneezing, shortness of breath, skin allergy and even cause forest fire. It is very attractive to discover ways for reducing the threats of poplar catkins to the environment and human health and even to convert poplar catkins into useful materials. Herein we report on a facile and cost-efficient strategy for the synthesis of hierarchical porous carbon microtubes using poplar catkins as the carbon source. The synthesis involves pre-carbonization and subsequent ZnCl 2 activation. The resultant materials not only inherit the natural tubular morphology of poplar catkins, but also develop a hierarchical porous structure, with nitrogen from the biomass being self-doped in the resultant carbon skeleton. The hierarchical porosity, especially the microporosity with the pore size from 0.5 to 1 nm, surface structure, tube wall thickness and nitrogen content can be readily controlled by adjusting the activation temperature and the ZnCl 2 -to-precursor mass ratio. The produced materials exhibit an excellent CO 2 capture capacity. The optimal sample activated at 800 °C with a ZnCl 2 -to-precursor mass ratio of 4:1 shows an extraordinarily high CO 2 adsorption capacity of 6.22 and 4.05 mmol g−1 at 273 and 298 K, respectively, at 1 bar of CO 2. Furthermore, the material also displays an excellent recyclability and CO 2 /N 2 selectivity. Our approach not only relieves the environmental pollution of poplar catkins but also leads to the production of a high-performance CO 2 adsorbent, which is promising for industrial CO 2 capture and separation. It therefore demonstrates an example of trash-to-treasure transformation. [ABSTRACT FROM AUTHOR]