Rational design of cobalt and nitrogen co-doped carbon hollow frameworks for efficient photocatalytic degradation of gaseous toluene

Abstract

In this work, the hollow Co/N co-doped carbon frameworks (Co/N-C) were successfully constructed by in situ transformation of zeolitic imidazolate frameworks (ZIF-67) through polycondensation of dopamine. The hollow and porous structure of Co/N-C was demonstrated by transmission electron microscopy (TEM). The doping and Co-N-C active sites were verified by X-ray photoelectron spectroscopy (XPS). The UV–vis diffusion reflectance spectra (UV–vis DRS) of hollow Co/N-C nanoparticles reflected a significant enhancement of optical absorption in the range of 300–800 nm. With hollow porous structure, strong optical absorption and rich Co-N-C active sites, the Co/N-C exhibited a high photocatalytic performance by using gaseous toluene as a model pollutant, and the degradation efficiency of gaseous toluene was found to be around 78.2% under mild conditions (i.e., Temperature = 273 K, Pressure = 1 atom, λ ≥ 420 nm, t = 6 h). The photocatalytic degradation process and mechanism of toluene were further investigated by in situ Fourier transform infrared (FTIR) spectroscopy, which indicated that multiple hydroxylation and benzen ring opening are both involved in the catalytic elimination processes, and the initial intermediate species including benzaldehyde and benzoic acid were firstly derived from the hydroxylation due to the hydroxyl radical followed by further oxidation into carbon dioxide and water.