Orientation controlled preparation of nanoporous carbon nitride fibers and related composite for gas sensing under ambient conditions

Creating pores in suprastructures of two-dimensional (2D) materials while controlling the orientation of the 2D building blocks is important in achieving large specific surface areas and tuning the anisotropic properties of the obtained functional hierarchical structures. In this contribution, we report that arranging graphitic carbon nitride (g-C₃N₄) nanosheets into one-dimensional (1D) architectures with controlled orientation has been achieved by using 1D oriented melem hydrate fibers as the synthetic precursor via a polycondensation process, during which the removal of water molecules and release of ammonia gas led to the creation of pores without destroying the 1D morphology of the oriented structures. The resulting porous g-C₃N₄ fibers with both meso- and micro-sized pores and largely exposed edges exhibited good sensing sensitivity and selectivity towards NO₂. The sensing performance was further improved by hybridization of the porous fibers with Au nanoparticles (Au NPs), leading to a detection limit of 60 ppb under ambient conditions. Our results suggest that the highly porous g-C₃N₄ fibers and the related hybrid structures with largely exposed graphitic layer edges are excellent sensing platforms and may also show promise in other electronic and electrochemical applications.