Solvent-free synthesis of highly dispersed zinc-doped porous carbons as efficient dibenzothiophene adsorbents

Designing efficient adsorbents for the deep removal of refractory dibenzothiophene (DBT) from fuel oil is vital for addressing environmental issues such as acid rain. Herein, zinc gluconate and urea-derived porous carbons SF-ZnNC-T (T represents the carbonization temperature) were synthesized without solvents. Through a temperature-controlled process of “melting the zinc gluconate and urea mixture, forming H-bonded polymers, and carbonizing the polymers,” the optimal carbon, SF-ZnNC-900, was obtained with a large surface area (2280 m² g^-1), highly dispersed Zn sites, and hierarchical pore structures. Consequently, SF-ZnNC-900 demonstrated significantly higher DBT adsorption capacity of 43.2 mg S g^-1, compared to just 4.3 mg S g^-1 for the precursor. It also demonstrated good reusability, fast adsorption rate, and the ability for ultra-deep desulfurization. The superior DBT adsorption performance resulted from the evaporation of residual zinc species, which generated abundant mesopores that facilitated DBT transformation, as well as the formation of Zn-N sites that strengthened the host-guest interaction (ΔE = -1.466 eV). The solvent-free synthesized highly dispersed Zn-doped carbon shows great potential for producing sulfur-free fuel oil and for designing metal-loaded carbon adsorbents.