Facile construction of N, P and O ternary self-doped hollow carbon microspheres with hierarchical porous structure for environmental applications

With the aim to develop novel adsorption materials for highly-efficient CO2 capture and organic dye removal, herein, N, P and O ternary self-doped hollow porous carbon microspheres (NPO-HPCSs) were fabricated via one-step direct carbonization of a single polymer precursor-crosslinked polyphosphazene. The morphology and microstructure of the NPO-HPCSs were characterized through TEM, SEM, XRD, XPS, FT-IR and N-2 sorption test. The influences of initial dye concentration, solution pH, temperature and contact time on malachite green (MG) adsorption were systematically studied. Furthermore, three dynamic models coupled with four isotherm models were employed to coordinate the experimental data. Results show that the NPO-HPCSs own high specific surface area of up to 2153.46 m(2) g(-1), hierarchical pore structure and high heteroatom content. Meanwhile, the NPO-HPCSs delivered remarkably adsorption capacity towards MG (972 mg g(-1) at 298 K), rapid adsorbing ratio (adsorption equilibrium time of 60 min), as well as excellent recycling stability. The outstanding adsorption performance of the NPO-HPCSs towards MG was attributed to the synergistic contribution of surface adsorption (electrostatic attraction, Lewis acid-base interaction and pi-pi stacking) and pore adsorption. Additionally, the NPO-HPCSs exhibited high CO2 capture capacities at atmospheric pressure: 2.84 mmol g(-1) at 298 K and 4.83 mmol g(-1) at 273 K, respectively.