Metal-Free Carbon Catalysts Derived From Industrial Lignin for Efficient Alcohols Oxidation

Abstract

A comprehensive understanding of the electronic structure of catalytic active centers and their nearby environments is essential for clarifying the link structure and activity. This understanding can facilitate the design and development of novel metal-free carbon-based materials with desirable catalytic properties from industrial lignin waste. In this research, phosphorus (P) or nitrogen (N) atoms are incorporated into sulfur (S)-doped porous carbon using a highly effective collosol doping carbonization method, which alters the electronic configuration of the active sites and enhances catalytic performance. The P and S co-doped porous carbon (SPC) demonstrates remarkable effectiveness in the oxidation of benzyl alcohol (BA), reaching a high conversion rate of 96.6% within 2 h and benzaldehyde (BAD) yield of 92.5%, along with a turnover frequency (TOF) value of 8.6 × 10⁻³ mol·g⁻¹·h⁻¹. It also exhibits strong catalytic selectivity for other functionalized alcohols. Density functional theory calculations (DFT) indicate that the incorporation of P or N atom into S-doped porous carbon increases the electron density at the Fermi level and modifies Mulliken charge distributions at the active sites, enhancing cooperative electron regulation and catalytic activity, particularly in the P and S co-doping structures. These findings offer guidance for the design of advanced metal-free carbon catalysts.