Elucidating Structural Stability, Bandgap, and Photocatalytic Hydrogen Evolution of (H₂O/DMF)@HKUST-1 Host-Guest Systems

The H₂O@HKUST-1 and DMF@HKUST-1 systems were experimental and computationally assessed, employing XRD/TGA/FT-IR/DFT-calculations, evidencing that H₂O or DMF coordinated to Cu, modulating HKUST-1 photocatalytic properties. DMF@HKUST-1 has narrower bandgap promoting higher-crystallinity and light-harvesting. H₂O@HKUST-1 showed smaller particle sizing and sharp morphology. Theoretical models, (H₂O)₁@HKUST-1 and (DMF)₁@HKUST-1, containing one coordinated molecule, elucidated bandgap modulation associated with infiltration. H₂O@HKUST-1/DMF@HKUST-1 presented bandgaps [eV] of 3.6/3.4, by Tauc plots, and 3.55/3.26, by theoretical calculations, narrowing bandgap, compared with non-solvated HKUST-1(HKUST-1_NS). Both composites raised the valence band (VB) and lowered the conduction band (CB), but DMF@HKUST-1 most raised VB. Topological analysis revealed that guests i) with higher electronic density, raised VB, and ii) induced π-backbonding, lowering CB. DMF@HKUST-1 presented a higher photocatalytic hydrogen evolution (μmol), 26.45, in the first 30 min of the reaction, nevertheless, H₂O@HKUST-1 presented a competitive activity, of 17.32. In large periods, H₂O@HKUST-1/DMF@HKUST-1 showed practically the same hydrogen evolution, 45.50/49.03.