Better Choice for a Polyimide Photocatalyst: Planar or Stereo Crosslinked Structures?

Polyimide photocatalysts with planar or stereo crosslinked structures are achieved by rational structure design, aiming to study structure influence on photocatalytic performance at the molecular level for better designing photocatalysts with good properties. The crosslinked structure is controlled by the configuration of two trifunctional amino monomers, 4,4′,4″-triaminotriphenylamine (TPA) and melamine (MA). 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) was chosen as the key anhydride unit to polycondense with the amino monomers for good visible light harvesting, charge-carrier mobility, and photo-stability. The structure and morphology of polyimide networks (T-PI for the TPA-NTCDA copolymer while M-PI for the MA-NTCDA copolymer) show that T-PI has a porous and amorphous texture with a specific surface area up to 70.2 m2/g, while M-PI exhibits flake-like and crystalline structure with a lower specific surface area of 20 m2/g. Interestingly, a superior performance on photo-degradation of RhB was witnessed by using M-PI as the photocatalyst, although T-PI possesses a smaller bandgap (1.65 eV), wider spectra response , and higher RhB adsorption capability under identical conditions. Combining photocatalytic activities with the stereo difference between M-PI and T-P, we rationally concluded that a planar crystalline texture could be a better choice for polyimide photocatalyst toward efficient elimination of environmental pollutants.