Tuning the Porosity and Photocatalytic Performance of Triazine-Based Graphdiyne Polymers through Polymorphism
Abstrakt
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 Cu-I for TzG(Cu) and Pd-II/Cu-I for TzG(Pd/Cu).
The polymers form through irreversible coupling reactions and give rise to a crystalline (TzG(Cu)) and an amorphous (TzG(Pd/Cu)) polymorph. Notably, the crystalline and amorphous polymorphs are narrow-gap semiconductors with permanent surface areas of 660 m(2) g(-1) and 392 m(2) 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 mu mol h(-1) g(-1) with and 276 mu mol 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.