N-Containing Carbon Materials in Metal-Free and Non-Noble Metal Liquid Phase Heterogenous Catalysis

Abstract

Non-noble metal and metal-free catalysts can be of great benefit for the development of economically and environmentally sustainable chemical processes. In this context, N-containing carbon materials serve both as effective catalyst supports and standalone catalysts, offering enhanced stability by mitigating deactivation mechanisms such as metal leaching and sintering. The review is primarily organized by non-noble metal, systematically covering each case in which their use as an active phase on N-containing carbon materials has been reported in literature. In parallel, cross-cutting aspects are examined throughout, including the role of different N-functionalities (graphitic, pyridinic, pyrrolic, and pyridinic-N-oxide) in active-phase stabilization mechanisms. Structurally diverse carbon materials—such as amorphous carbon, carbon nanotubes, carbon spheres, carbon nanofibers, and graphene—are also considered. Furthermore, the influence of preparation methods, including template-free, hard-templating and soft-templating techniques, is analyzed with emphasis on their role in tuning textural properties. Despite significant progress, uncertainties remain regarding the precise stabilization mechanisms and the relative contributions of different N-functionalities to catalytic activity and surface acid–base properties. Addressing these knowledge gaps will be essential for optimization of N-containing carbon materials and to drive the transition towards greener and more sustainable catalytic technologies.