Hydrogen-Bonding Strategy Advances CO2-to-Fuel Electrocatalysis

Researchers have developed a novel catalyst design that stabilizes key intermediates in CO₂ reduction, significantly boosting efficiency.

Catalytic conversion of waste CO₂ into value-added fuels and chemicals presents major opportunities for environmental sustainability and economic growth. Among the emerging strategies, the electrocatalytic CO₂ reduction reaction (CO₂RR) has attracted growing attention for its ability to efficiently convert CO₂ into clean chemical energy under relatively mild conditions. However, one of the main challenges remains the high energy barrier associated with forming the *COOH intermediate—often the rate-determining step in CO₂RR—leading to reduced overall efficiency.

Drawing inspiration from enzyme catalysis, a research team led by Prof. JIANG Hai-Long and Prof. JIAO Long at the University of Science and Technology of China (USTC), under the Chinese Academy of Sciences (CAS), has developed an innovative approach to enhance CO₂ electroreduction. By designing and tuning the hydrogen-bonding microenvironment around catalytic sites, the team successfully stabilized the *COOH intermediate and boosted reaction performance. Their findings were recently published in Proceedings of the National Academy of Sciences.

In this study, the researchers co-grafted catalytically active Co(salen) units and pyridyl-substituted alkyl carboxylic acids (X-PyCn) onto Hf-based MOF nanosheets (MOFNs) using a post-synthetic modification method. The resulting materials—designated Co&X-PyCn/MOFNs (with X = o, m, or p denoting the pyridine nitrogen's position and n = 1 or 3 indicating the length of the alkyl chain)—allowed for precise spatial control of the pyridine nitrogen atoms relative to the Co(salen) centers. This atomic-level control offered a powerful tool to fine-tune the local catalytic environment.

Among the series, Co&p-PyC3/MOFNs emerged as the top performer, demonstrating significantly enhanced catalytic activity and selectivity for CO₂ reduction compared to both unmodified Co/MOFNs and other X-PyCn variants.

A key discovery in this work was the in situ formation of pyridinyl radicals (PyrH•) during the electrochemical process. These PyrH• species were shown to be essential in creating the effective microenvironment that drives the enhanced catalytic performance.

Further mechanistic analysis revealed that PyrH• interacts synergistically with trifluoroethanol (TFE) in the electrolyte, stabilizing the *COOH intermediate through the formation of a hydrogen-bonded *COOH···TFE···PyrH• triad. This interaction effectively lowers the reaction’s energy barrier and sheds new light on how local chemical environments influence catalytic behavior.

This study highlights the critical role of microenvironment modulation in advancing catalytic efficiency and offers a promising direction for future research into catalyst design and mechanism exploration.

Journal Reference:

Yang, G., et al. (2025) In situ generated hydrogen-bonding microenvironment in functionalized MOF nanosheets for enhanced CO₂ electroreduction. Proceedings of the National Academy of Sciences. doi.org/10.1073/pnas.2419434122