Dendritic Fibrous Nanosilica Coated with a Graphitic Carbon Nitride Shell as a Selective Catalyst for N‑Dealkylation

KCC-1@g-C₃N₄ composites, synthesized via thermal condensation of the melamine-cyanuric acid (MCA) complex on mesoporous KCC-1 silica nanoparticles, were developed with g-C₃N₄ content ranging from 7 to 45 wt %. Characterization by SEM, STEM, FTIR, XPS, and UV-vis DRS revealed a core-shell structure with band gaps of 2.82 and 2.86 eV and specific surface areas of 167.5-526.8 m²/g. These composites were evaluated as photocatalysts for the transformation of rhodamine B under visible light. At low g-C₃N₄ content (7-33 wt %), the composites selectively promote N-dealkylation, converting rhodamine B to rhodamine-110, as confirmed by UV-vis spectroscopy and mass spectrometry MALDI-TOF. Higher g-C₃N₄ content (38-45 wt %) leads to chromophore destruction, resembling pure g-C₃N₄ behavior. The enhanced N-dealkylation selectivity at lower g-C₃N₄ ratios is attributed to efficient charge separation facilitated by KCC-1 impurity electronic levels and the defects in the g-C₃N₄ shell. These findings highlight the potential of KCC-1@g-C₃N₄ composites for selective photocatalytic transformations, offering applications in environmental remediation and organic synthesis.