  The supramolecular preorganization approach can be applied to effectively
fabricate various morphologies of graphitic carbon nitride(g-CN)with improved
photocatalytic activity, while a comprehensive understanding for the morphology
evolution from supramolecular aggregates to g-CNs is lacking. Herein, 3D
characterizations from electron tomography provide a fundamental insight on the
evolution from rod-like melamine-cyanuric acid(MC)complex to hollow-structure
g-CN in the thermal polycondensation process. The internal region and a group
of surfaces of the rod-like complex initially underwent polycondensation, while
the other two groups of surfaces with ~100 nm thickness almost unchanged. With
the temperature reached to 550 degree C, the hollow-structure g-CN eventually
formed due to most of the internal matter vanishing, and voids arose in the
previously unaffected surfaces(edges),resulting in a porous shell structure.
Quantitative electron tomography indicates that the key of structure evolution
is the differentiated condensation polymerization between edges and inner
region of the rod-like MC complex, which is ascribed to a higher dense of
surfaces and a lower dense of inner matter with loose, defective orignization.
