1. Molecular engineering in tunable crystallinity of 2D covalent organic frameworks for efficient photocatalytic hydrogen evolution.
- Author
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Xiao, Yueyuan, Wang, Kuixing, Dong, Wenbo, and Li, Longyu
- Subjects
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METAL-organic frameworks , *HYDROGEN evolution reactions , *CRYSTALLINITY , *INTERSTITIAL hydrogen generation , *HYDROGEN , *HYDROGEN production , *STACKING interactions - Abstract
The strategy of molecular engineering has been employed to build the structure–property–activity relationship for covalent organic frameworks (COFs) with efficient photocatalytic water splitting for hydrogen production. However, previous reports focus on the impact of molecular design on COFs' physicochemical properties, the crystallinity differences are usually ignored and related studies remain rare. Herein, we describe the preparation of a series of structurally related COFs with similar chemical compositions but have different numbers of nitrogen (N) atoms in the central aromatic ring via an efficient crystallization strategy using of 2,4,6-triformyl resorcinol (TFR). On one hand, the introduction of N atoms reduces π-π stacking interaction during the formation of framework, leading to a decrease in crystallinity. On the other hand, it contributes to enhancing the photocatalytic performance of the materials by varying the electronic structures. Consequently, our results revealed that the photocatalytic hydrogen evolution (PHE) rate is 61.22 mmol g−1 h−1 for COF-905-1N, significantly higher than COF-905-3N (40.60 mmol g−1 h−1) and COF-905 (26.23 mmol g−1 h−1). This study not only provide fundamental insights into formation mechanism of COFs, but also provide a practical approach to enhance COF-based photocatalytic performance. We synthesized three COFs (COF-905, COF-905-1N, and COF-905-3N) with varying number of nitrogen atoms, resulting in different crystallinity via molecular engineering. COF-905-1N shows the highest photocatalytic hydrogen production performance with a rate up to 61.22 mmol g−1 h−1. The water-drainage experiments also suggest the potential of COF-905-1N in the practical applications for photocatalytic hydrogen evolution. [Display omitted] • Three structurally related COFs were constructed via an efficient crystallization strategy based on the use of TFR. • The crystallinity of the resultant COFs decreases as the number of N atoms in the central benzene ring increases. • The π-π stacking between the intermediate macrocycles becomes less favorable, leading to incompact stacking of 2D layers. • COF-905-1N exhibits superior PHE performance under the combined influence of nitrogen content and crystallinity. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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