Covalent Organic Framework–Carbon Nanotube Core–Shell Nanohybrids for Enhanced Catalytic Site Utilization of Molecular Catalysts in CO ₂ Electroreduction

Developing strategies to enhance the utilization efficiency of catalytic sites in molecular catalysts has garnered increasing research interest in the field of molecular heterogeneous catalysis. The primary challenges in achieving this goal lie in the aggregation-induced site inaccessibility in molecular catalysts. Here, we present the synthesis of covalent organic framework-carbon nanotube (COF-CNT) core-shell nanohybrids as a platform to improve the site utilization of molecular catalysts in electrochemical CO₂ reduction. COF shells with a thickness of 50-80 nm are uniformly grown on CNTs, ensuring a well-defined morphology with pores oriented perpendicularly to the CNT basal plane. The incorporation of molecular catalysts with COF-CNT nanohybrids enables their application as scaffolds in the electrochemical CO₂ reduction. The best-performing sample exhibits a two-orders-of-magnitude increase in CO turnover frequency (TOF) compared to both pristine CoTPyP molecular catalyst and COF-366-Co, thus underscoring the effectiveness of the COF-CNT hybrid structure in optimizing catalytic site accessibility. The enhanced site utilization is further validated in other molecular catalyst systems, where exceptionally high TOF values-among the highest reported to date for electrochemical CO₂-to-CO conversion-were achieved. Collectively, this study establishes COF-CNT nanohybrids as a promising strategy for advancing COF-based electrocatalysts and facilitating molecular catalyst applications in electrochemical energy conversion.