Tuning the porosity and photocatalytic performance of triazinebased graphdiyene polymers via polymorphism

Schwarz, D.; Amitava, A.; Ichangi, A.; Kochergin, Y. S.; Lyu, P.; Opanasenko, M. V.; Tarábek, J.; Vacek Chocholoušová, J.; Vacke, J.; Schmidt, J.; Nachtigall, P.; Thomas, A.; Bojdys,* M. J. ChemSusChem 2018, accepted article, DOI: 10.1002/cssc.201802034 [OPEN ACCESS]

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, we present two porous polymorphs of a triazine-based graphdiyene (TzG) framework from a simple, one-pot reaction using Cu(I) for TzGCu and Pd(II)/Cu(I) for TzGPd/Cu catalyzed homocoupling polymerization. The polymers form via 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 thus far up to 972 μmol h-1 g-1 with and 276 μmol h-1 g-1 without Pt co-catalyst. We conclude, that crystalline order improves delocalisation, while the amorphous polymorph requires a co-catalyst for efficient charge transfer; this will need to be considered in future rational design of polymer catalysts and organic electronics.

DOI: 10.1002/cssc.201802034