Computational studies of NH2-MIL-125(Ti): stability, electronic structure and defects

The urgent need to mitigate water contamination and greenhouse gas emissions has driven the search for efficient photocatalysts. Metal–organic frameworks (MOFs) are attractive in this context due to their high porosity and structural tunability, and the amino-functionalized titanium MOF NH2-MIL-125(Ti) stands out for its chemical stability, visible-light absorption, and ligand-to-metal charge-transfer (LMCT) character. This thesis presents a DFT study of NH2-MIL-125(Ti) and five derivatives, examining how metal-node sub stitutions and linker functionalization tune their electronic structure and photocatalytic suitability. Cu and Zr are introduced at the node (single-site Cu at two non-equivalent Ti positions, single-site Zr, and full Zr substitution) because Cu is earth-abundant, low-cost, and more electronegative than Ti, while Zr dopants are reported to reduce charge recombination; Cl is used as an electron-withdrawing substituent replacing–NH2 on the linker. All structures are relaxed with the PBEsol functional, band gaps and projected densities of states are computed using PBEsol/mBJ, and absolute band-edge positions are obtained by referencing Kohn–Sham eigenvalues to a vacuum level defined by the electrostatic potential at the pore centre. The pristine framework shows a visible band gap with a linker-derived valence band and Ti d-dominated conduction band. Cusubstitutionmainlyraisesthevalence-bandmaximumandnarrowsthegap. Clfunctionalisation leaves the gap almost unchanged, full Zr substitution slightly widens the gap and shifts band edges to more negative potentials, and a single Zr defect produces a smaller gap and lower work function due to low-lying Zr d-states. Vacuum-level alignment indicates that all systems except the Zr-defect structure satisfy the thermodynamic criteria for overall water splitting at pH 7 and therefore remain promising photocatalysts. Future work will combine spin-polarised DFT, Bader/protonation analyses, hybrid (HSE06) benchmarks, and adsorption/reaction modelling for HER, OER, and CO2 reduction on the most promising doped nodes.

• Главный автор: González Tamayo, Emily Antonella (author)
• Формат: bachelorThesis
• Опубликовано: 2026
• Предметы: Fotocatálisis; Brecha de banda; Photocatalysis; Band gap
• Online-ссылка: https://repositorio.yachaytech.edu.ec/handle/123456789/1051