Covalent Triazine Frameworks as Emerging Heterogeneous Photocatalysts

Abstract

Covalent triazine frameworks (CTFs) have attracted a great deal of attention as an attractive new class of visible light-active, metal-free, and polymer-based heterogeneous photocatalysts. CTFs have demonstrated promising characteristics such as synthetic diversity, stability, nontoxicity, pure organic nature, and enhanced ordered structure. In this review, we aim to summarize the recent developments in CTFs ranging from novel preparation methods to critical factors that directly impact their photocatalytic efficiency. Various physical and chemical design strategies for morphology, band structure, charge separation, and transfer optimization described in the literature are discussed. Emphasis is placed on the enhancement and maximization of photocatalytic efficiencies of specific applications such as photoredox organosynthesis, water splitting, CO2 photoreduction, H2O2 generation, etc.

Advances in porous organic polymers: syntheses, structures, and diverse applications

“…CTFs are partially crystalline, amorphous porous materials possessing conjugated and layered structures. 66 Thomas and co-workers were the first to report examples of CTF materials containing aromatic rings and triazine moieties in the core. 6 CTFs have attracted much attention for their potential applications in, for example, CO 2 reduction, pollutant degradation, organosynthesis, water splitting, H 2 O 2 and H 2 production, and organic semiconductor devices.…”

“…[67][68][69][70][71][72] Several approaches have been used for the preparation of CTFs, including cyclotrimerization of nitrile groups through direct or indirect methods in the presence of molten ZnCl 2 at 400 °C; superacid-catalyzed trimerization; Suzuki cross-coupling; Nicatalyzed Yamamoto coupling; and P 2 O 5 catalysis at 400 °C (Figure 3). 66 The preparation of CTFs with 6 highly crystalline structures requires choosing monomers with planar characteristics; the use of nonplanar monomers leads to the formation amorphous or semicrystalline CTFs. [73][74][75][76] To date, only a few crystalline CTFs have been reported.…”

Organic materials as photocatalysts for water splitting

“…31 Covalent triazine-based frameworks (CTFs) are related to carbon nitrides in their high nitrogen content but are (unlike carbon nitrides) accessible using low temperatures using acidcatalysed trimerisation reactions or Suzuki-Miyaura type polycondensation reactions. 32 CTFs are able to facilitate photocatalytic hydrogen evolution from water, with platinum co-catalysts and in the presence of sacrificial agents. A large Please do not adjust margins number of structurally diverse CTFs has been reported to be active 24,33 with quantum yields as high as 15.9% at 420 nm under sacrificial conditions.…”

Light-Driven Hydrogen Evolution Assisted by Covalent Organic Frameworks

“…Another example can be found in the condensation reaction between 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (also named 1,3,5-triformylphloroglucinol, TP) and 3,9-diamino-benzo[1,2-b:4,5-b ]bis [1]benzothiophene sulfone (Figure 2b), involving the formation of a Schiff base between the aldehyde and the amino groups after dehydration, and the subsequent irreversible enol-to-keto conversion to form the β-ketoenamine-linked FS-COF [24] (Figure 4d) containing the sulfone functional groups (FS stands for fused sulfone). Additionally, covalent triazine framework (CTF)-based COFs are among the most relevant photocatalytic examples, whose properties will be discussed later [31]. CTF-COFs can be synthesized under mild conditions by condensation at 120 • C of aldehydes (e.g., 1,4-benzenedialdehyde, Figure 2c) and amidines (e.g., terephthalimidamide, Figure 2c) involving the formation of a Schiff base between the aldehyde and the amidine groups after dehydration, followed by a Michael addition reaction to form the triazine ring after the elimination of ammonia (Figure 2c) [20,21].…”