Abstract
Poly(triazine imide) or PTI is an ordered graphitic carbon nitride hosting Å-scale pores attractive for selective molecular transport. AA'-stacked PTI layers are synthesized by ionothermal route during which ions occupy the framework and occlude the pores. Synthesis of ion-free PTI hosting AB-stacked layers has been reported, however, pores in this configuration are blocked by the neighboring layer. The unavailability of open pore limits application of PTI in molecular transport. Herein, we demonstrate acid treatment for ion depletion which maintains AA' stacking and results in open pore structure. We provide first direct evidence of ion-depleted open pores by imaging with the atomic resolution using integrated differential phase-contrast scanning transmission electron microscopy. Depending on the extent of ion-exchange, AA' stacking with open channels and AB stacking with closed channels are obtained and imaged for the first time. The accessibility of open channels is demonstrated by enhanced proton transport through ion depleted PTI.
K.V.A acknowledges Swiss National Science Foundation (SNSF) Project (20021_192005) for providing financial support for the chemistry of PTI. We also acknowledge the European Synchrotron Radiation Facility for provision of beam time on BM01 and we would like to thank Dr. Dmitry Chernyshov and Dr. Vadim Dyadkin for assistance. We thank Dr. Claudia Avalos for supporting preliminary solid-state NMR measurements, Dr. Natalia Gasilova for supporting ICP-OES, and Dr. Roxane Moinat for supporting CHNS analysis at EPFL. We would also like to thank Prof. Wolfgang Schnick’s group at University of Munich for the CIF file of the PTI crystal.