Pyrazine‐Functionalized Donor–Acceptor Covalent Organic Frameworks for Enhanced Photocatalytic H₂ Evolution with High Proton Transport

Abstract

The well‐defined 2D or 3D structure of covalent organic frameworks (COFs) makes it have great potential in photoelectric conversion and ions conduction fields. Herein, a new donor–accepter (D–A) COF material, named PyPz‐COF, constructed from electron donor 4,4′,4″,4′″‐(pyrene‐1,3,6,8‐tetrayl)tetraaniline and electron accepter 4,4′‐(pyrazine‐2,5‐diyl)dibenzaldehyde with an ordered and stable π‐conjugated structure is reported. Interestingly, the introduction of pyrazine ring endows the PyPz‐COF a distinct optical, electrochemical, charge‐transfer properties, and also brings plentiful CN groups that enrich the proton by hydrogen bonds to enhance the photocatalysis performance. Thus, PyPz‐COF exhibits a significantly improved photocatalytic hydrogen generation performance up to 7542 µmol g−1 h−1 with Pt as cocatalyst, also in clear contrast to that of PyTp‐COF without pyrazine introduction (1714 µmol g−1 h−1). Moreover, the abundant nitrogen sites of the pyrazine ring and the well‐defined 1D nanochannels enable the as‐prepared COFs to immobilize H3PO4 proton carriers in COFs through hydrogen bond confinement. The resulting material has an impressive proton conduction up to 8.10 × 10−2 S cm−1 at 353 K, 98% RH. This work will inspire the design and synthesis of COF‐based materials with both efficient photocatalysis and proton conduction performance in the future.

Donor–acceptor hetero[6]radialene-based three-dimensional covalent organic frameworks for organic pollutant adsorption, photocatalytic degradation, and hydrogen production activity

“…Overall, our TFP-BF 3D COF photocatalyst demonstrated remarkable photocatalytic performance for water reduction to generate H 2 , both with and without the inclusion of additional co-catalysts. The TFP-BF 3D COF has the highest photocatalytic HER efficiency among numerous COF-based photocatalysts including thiazolo[5,4- d ]thiazole-based COF (PyTz-COF, 2.07 mmol g −1 h −1 ), 100 vinylene-bipyridine-based COF (COF-BPDA, 3.23 mmol g −1 h −1 ), 101 bicarbazole-based COF (PyTA-BC COF, 5.03 mmol g −1 h −1 ), 5 benzotrithiophene-based COF (BTT-NDA COF, 5.22 mmol g −1 h −1 ), 102 pyrazine-based COF (PyPz COF, 7.54 mmol g −1 h −1 ), 60 benzo-2,1,3-thiadiazole-based COF (BT-COF, 7.70 mmol g −1 h −1 ), 103 platinum-2,4,6-triformylphloroglucinol-based COF (Pt-PVP-TP, 8.42 mmol g −1 h −1 ), 104 chloride-benzothiadiazole-based (Py-ClTP-B, 8.87 mmol g −1 h −1 ), 105 sulfone (FS)-based COF (10.10 mmol g −1 h −1 ), 95 pyrazine-polyethylene glycol-based COF (30 EG@BTCOF, 11.14 mmol g −1 h −1 ), 103 benzothiazole-based COF (NKCOF-108, 11.60 mmol g −1 h −1 ), 106 benzotrithiophene-bipyridine-based COF (BTT-BPy-PCCOF, 12.30 mmol g −1 h −1 ), 107 sp 2 -benzobisthiazole-based COF (BTH-3 COF, 15.10 mmol g −1 h −1 ), 108 sound-based COF (SonoCOF-3, 16.60 mmol g −1 h −1 ) 109 (Fig. 8d and Table S12†).…”

“…They have typically featured limited numbers of donor and acceptor units—namely tris(4-aminophenyl)amine, pyrene, porphyrin, tetraphenylethylene, benzobisthiazole, and benzotrithiophene as electron donors, and tetraphenylethylene, pyrazine, triazine, thiadiazole, thiazolo[5,4- d ]thiazole, and phloroglucinol units as electron acceptors. 60–65 In addition, only a report has been mentioned using 3D COF as a photocatalyst to degrade organic pollutants. 66 Hence, creating environmentally friendly donor and acceptor 3D COFs as semiconductor materials for the adsorption and photocatalytic degradation of natural dyes in aqueous solutions and the production of hydrogen from water remains a formidable undertaking.…”

Molecular engineering of donor–acceptor sp2-carbon-linked covalent organic frameworks for enhancing photocatalytic hydrogen production

“…4b, all three COFs exhibited photoactivity toward hydrogen evolution, especially TTh-COF, which reached a higher HER of 22.22 mmol h −1 g −1 , and the value outperformed those of most previously reported D–A COFs. 52–57 In contrast to TTh-COF, Ph-COF displayed a relatively low hydrogen evolution rate (HER) of 3.48 mmol h −1 g −1 . Although Th-COF and TTh-COF both possess thiophene units, Th-COF exhibited an HER of only 15.58 mmol h −1 g −1 , and the difference is attributed to the strong electron donating ability of benzothiophene and the narrow band gap of TTH-COF.…”

Proton Conduction Properties of Intrinsically Sulfonated Covalent Organic Framework Composites

“…Table S2: Fractional atomic coordinates for the unit cell of TpPa. Table S3: Fractional atomic coordinates for the unit cell of TpPa-SO 3 H. Table S4: Humidity-dependent proton conductivity (S cm −1 ) of TpPa, TpPa@H 2 SO 4 , TpPa-SO 3 H, and PANa@TpPa-SO 3 H. Table S5: Temperature-dependent proton conductivity (S cm −1 ) of TpPa, TpPa@H 2 SO 4 , TpPa-SO 3 H, and PANa@TpPa-SO 3 H. References [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] are cited in the supplementary materials.…”