Tuning the Porosity and Photocatalytic Performance of Triazine‐Based Graphdiyne Polymers through Polymorphism

Abstract

Crystalline and amorphous organic materials are an emergent class of heterogeneous photocatalysts for the generation of hydrogen from water, but a direct correlation between their structures and the resulting properties has not been achieved so far. To make a meaningful comparison between structurally different, yet chemically similar porous polymers, two porous polymorphs of a triazine‐based graphdiyne (TzG) framework are synthesized by a simple, one‐pot homocoupling polymerization reaction using as catalysts CuI for TzGCu and PdII/CuI for TzGPd/Cu. The polymers form through irreversible coupling reactions and give rise to a crystalline (TzGCu) and an amorphous (TzGPd/Cu) polymorph. Notably, the crystalline and amorphous polymorphs are narrow‐gap semiconductors with permanent surface areas of 660 m2 g−1 and 392 m2 g−1, respectively. Hence, both polymers are ideal heterogeneous photocatalysts for water splitting with some of the highest hydrogen evolution rates reported to date (up to 972 μmol h−1 g−1 with and 276 μmol h−1 g−1 without Pt cocatalyst). Crystalline order is found to improve delocalization, whereas the amorphous polymorph requires a cocatalyst for efficient charge transfer. This will need to be considered in future rational design of polymer catalysts and organic electronics.

Solving the COF trilemma: towards crystalline, stable and functional covalent organic frameworks

“…Multiple additions with less internal linking could be likened to a dendrimer type growth of the structure that leads to a reduction in order, because the building block addition can trap the incompatible conformer. 103 The possibility of dendrimer type growth depends on the flexibility and possible Fig. 16 Overview of the reactions used to lock the imine linkage.…”

“…The irreversible Glaser coupling can be used to obtain ordered materials if the feed rate and hence the reaction rate is slowed down. 103 This was shown by using two different reaction protocols that differ significantly in their reaction rates: a Glaser coupling based on copper(I) chloride and a Sonogashira-like coupling catalysed by palladium. While the faster reaction catalysed by palladium yielded only an amorphous polymer, it was possible to obtain a somewhat ordered material with the slower Glaser coupling.…”

Real-time optical and electronic sensing with a β-amino enone linked, triazine-containing 2D covalent organic framework

“…Their use in sensing applications and electrochemical devices has been hampered by the poor stability of these early COFs. We recently reported triazine (C 3 N 3 )-based graphdiyene frameworks that are not only crystalline but also stable with respect to a wide range of chemicals and temperatures and that show interesting photocatalytic and electronic effects as well as structural polymorphism 17,18 .…”

Multifunctional Visible‐Light Powered Micromotors Based on Semiconducting Sulfur‐ and Nitrogen‐Containing Donor–Acceptor Polymer

“…The FTIR spectrum of the SNP micromotors shows two distinctive features at ≈1500 and ≈820 cm −1 which correspond to C 3 N 3 ‐ring vibrations and stretching, respectively (Figure S3, Supporting Information). [ 31 ] Notably, the absence of NH‐ and OH‐stretching modes in the region around 3000 cm −1 , characteristic to some hydrolyzed fragments of the polymer, confirm the completion of the network‐forming condensation reaction. The SEM imaging reveals the irregular shape of SNP‐MMs, which is a consequence of a random nucleation growth, typical for bulk transition metal‐catalyzed reactions, such as Stille coupling (Figure 1b; and Figure S4, Supporting Information).…”