Strong‐Base‐Assisted Synthesis of a Crystalline Covalent Triazine Framework with High Hydrophilicity via Benzylamine Monomer for Photocatalytic Water Splitting

Abstract

Methods to synthesize crystalline covalent triazine frameworks (CTFs) are limited and little attention has been paid to development of hydrophilic CTFs and photocatalytic overall water splitting. A route to synthesize crystalline and hydrophilic CTF‐HUST‐A1 with a benzylamine‐functionalized monomer is presented. The base reagent used plays an important role in the enhancement of crystallinity and hydrophilicity. CTF‐HUST‐A1 exhibits good crystallinity, excellent hydrophilicity, and excellent photocatalytic activity in sacrificial photocatalytic hydrogen evolution (hydrogen evolution rate up to 9200 μmol g−1 h−1). Photocatalytic overall water splitting is achieved by depositing dual co‐catalysts in CTF‐HUST‐A1, with H2 evolution and O2 evolution rates of 25.4 μmol g−1 h−1 and 12.9 μmol g−1 h−1 in pure water without using sacrificial agent.

Modulating Benzothiadiazole‐Based Covalent Organic Frameworks via Halogenation for Enhanced Photocatalytic Water Splitting

“…Covalent organic frameworks (COFs) [6][7][8][9][10][11][12][13] with high crystallinity have emerged as promising alternatives to inorganic semiconductors for photocatalytic water splitting. [14,15] Recently, to achieve highly photoactive COFs toward efficient sunlight-driven H 2 conversion, many strategies [16][17][18][19][20][21][22][23][24][25][26] on improving photon capture and facilitating charge carrier separation have been developed through integrating various novel p-conjugated building blocks, [18] utilizing proper donor-acceptor (D-A) combinations [16,17,19,22] and depositing new co-catalysts.…”

Light-Driven Hydrogen Evolution Assisted by Covalent Organic Frameworks

“…There are more examples in the literature demonstrating that the photocatalytic HER is improved with an increased crystallinity of the COF scaffold. This is the case for the two following works of Tan et al dealing with CTF-COFs [20,22]. In the first example [20], the substitution of an aldehyde precursor by its corresponding alcohol analogue led to a decrease in the reaction rate of formation of the triazine-based COFs.…”

“…This includes both the organic part (COF) and the metallic (co-catalyst) part. Regarding the former, during the last 6 years it has been made clear that imine-derived [18], triazine-containing [9,[19][20][21][22], diacetylene-containing [23], β-ketoenamine-derived [23][24][25], and fully π-conjugated sp 2 C [26][27][28] COFs are very resistant under Despite the thermodynamic and kinetic aspects related to the photocatalytic process itself described above, the stability and fate of the whole system under turnover conditions cannot be disregarded. This includes both the organic part (COF) and the metallic (co-catalyst) part.…”

“…This includes both the organic part (COF) and the metallic (co-catalyst) part. Regarding the former, during the last 6 years it has been made clear that imine-derived [18], triazine-containing [9,[19][20][21][22], diacetylene-containing [23], βketoenamine-derived [23][24][25], and fully π-conjugated sp 2 C [26][27][28] COFs are very resistant under photocatalytic conditions, in contrast to the great tendency towards hydrolysis of boroxine and boronic ester-derived COFs [2,29]. Additionally, N-rich COFs have arisen as highly crystalline, porous, and chemically stable materials, showing enhanced lightharvesting and charge separation properties [14,29,30].…”

“…For example, when combined with Pt as co-catalyst, the crystalline CTF-HUST-C1 (Figure 4b) displayed a 4.75-fold increase in the H 2 evolution rate than its corresponding low-crystalline analogue, CTF-HUST-1. In the second example [22], the same CTF-COF was synthesized starting from the 1,4-phenylenedimethanamine precursor instead of the previous aldehyde or alcohol precursors, which in the presence of a strong base ( t BuOK) produced in a high yield (99.2%) the highly crystalline and hydrophilic (wettable) CTF-HUST-A1 COF. By using Pt as co-catalyst and TEOA as SED, this system displayed a 6.3-fold increase in the hydrogen evolution rate compared with CTF-HUST-1, that is, 9.2 mmol H 2 •g −1 •h −1 , and a high AQE of 7.4% at 420 nm.…”