The precise engineering of vacancies in nitrogen-doped graphene (NG) presents a promising strategy for stabilizing metal single-atom catalysts (SACs) and tuning their catalytic performance. We explore the role of vacancies in NG for stabilizing iron-based SACs (Fe-SACs) by using density functional theory (DFT). First, we examine the stability of various vacancy types in graphene and NG supports, addressing the question of preferential formation of specific structural defects as potential sites for metal binding. We reveal simple rules governing the stability of vacancies and show that nitrogen doping can bring about vacancy healing. We identify preferred binding sites for Fe atoms/ions, specifically single and double vacancies, and analyze how the nitrogen-doping pattern in a vacancy affects the interaction of Fe with the SAC support. The results show that the positions of nitrogen(s) and the local charge environment significantly influence the stability of the Fe-SACs. Notably, some Fe@NG configurations, although not the most thermodynamically stable, exhibit enhanced catalytic performance, particularly for a CO2 reduction reaction (CO2RR). These findings offer valuable insights into vacancy engineering as a strategy for designing high-performance Fe-SACs and emphasize the interplay among vacancy types, nitrogen concentration, and catalyst stability in driving the catalytic behavior.

• Klíčová slova
• Activity, CO2RR, SAC, Single-atom catalysis, Stability,
• Publikační typ
• časopisecké články MeSH

Benzamides constitute an important class of bulk and fine chemicals as well as essential parts of many life science molecules. Currently, all these compounds are majorly produced from petrochemical-based feedstocks. Notably the selective aerobic oxidative conversion of lignin and lignin-derived compounds to primary, secondary, and tertiary amides and phenols offers the potential for a more sustainable synthesis of valuable building blocks for fine chemicals, monomers for polymers, biologically active molecules, and diverse consumer products. Here we present the concept of "lignin to amides" which is demonstrated by a one-pot, multi-step oxidation process utilizing molecular oxygen and a 3d-metal catalyst with highly dispersed and stable cobalt species (Co-SACs) supported on nitrogen-doped carbon in water as solvent. Moreover, our cobalt-based methodology allows for the cost-efficient transformation of a lignin and its variety of derivates simply using O2 and organic amines. Mechanistic investigations and control experiments suggest that the process involves an initial dehydrogenation of Cα-OH, cleavage of the Cβ-O as well as C(O)-C bond and condensation of the resulting carboxylic acids with amines. Spectroscopic studies indicate that the formation of superoxide species (O2●-) and specific Co-nitrogen sites anchored on mesoporous carbon sheets are key for the success of this transformation.

• Publikační typ
• časopisecké články MeSH