Metal-free N-doped spongy carbon recycled from waste MOF for enhanced catalytic ozonation: Mechanistic insights and practical applications

Abstract

At present, considerable efforts have been devoted to the development and application of MOFs, and some MOFs have realized industrial mass production and sales. However, little attention was paid to the treatment and disposal of the resulting waste MOF. In this study, the antibiotic(N source)-saturated waste MOF adsorbent was recycled into metal-free N-doped carbocatalyst through one-step pyrolysis. Compared with the pristine MOF-derived undoped carbon, N-doping led to nearly 2-fold enhancement in the pseudo-first-order rate constant for catalytic ozonation of oxalic acid (OA), and the COD removal of coking and swine wastewaters reached more than 60 % within 30 min. Apart from the formation of spongy porous morphology and the boosting of specific surface area from 253.7 to 320.6 m2/g after N doping, the characterization analysis and OA degradation results revealed that oxygen vacancies, hydroxyl groups and N species were the main active sites. Furthermore, it was identified the dominant contribution of OH in OA destruction, followed by O2— and 1O2, and the metal-free N-doped carbon displayed good reusability and chemical stability. This study proposes a feasible strategy for the utilization of waste MOF, showing great reference significance for the expansion of material functions.