Exploring the Structure–Property Relationship in Montmorillonite–Carbon Quantum Hybrid Nanomaterials Combining montmorillonite (MMT), a layered silicate clay, with carbon quantum dots (CQD) is a promising strategy to develop hybrid nanomaterials with enhanced and tunable properties. In this work, we explore the structure–property relationships in montmorillonite–carbon quantum dot (MCQD) hybrid nanomaterials synthesized through two distinct routes. In Route 1, pre-synthesized CQDs using citric acid and urea as precursors were physically mixed with MMT, giving rise to MCQD-R1 hybrid nanomaterials. In Route 2, MMT was added in situ in the CQD reaction medium before thermal treatment, with contact times from 1 to 16 h, generating MCQD-R2-1 and MCQD-R2-16, respectively. Structural and spectroscopy techniques were employed to investigate the resulting hybrids. PXRD analysis revealed that the synthesis conditions preserved the crystalline structures of both CQD and MMT clay. The FT-IR indica...