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Plasma‐Induced Defects Enhance the Visible‐Light Photocatalytic Activity of MIL‐125(Ti)‐NH 2 for Overall Water Splitting
Author(s) -
CabreroAntonino María,
Albero Josep,
GarcíaVallés Cristina,
Álvaro Mercedes,
Navalón Sergio,
García Hermenegildo
Publication year - 2020
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202003763
Subject(s) - photocatalysis , x ray photoelectron spectroscopy , crystallinity , materials science , water splitting , thermogravimetric analysis , oxygen , diffuse reflectance infrared fourier transform , analytical chemistry (journal) , photochemistry , nuclear chemistry , chemical engineering , chemistry , catalysis , organic chemistry , composite material , engineering
Defect engineering in metal‐organic frameworks is commonly performed by using thermal or chemical treatments. Herein we report that oxygen plasma treatment generates structural defects on MIL‐125(Ti)‐NH 2 , leading to an increase in its photocatalytic activity. Characterization data indicate that plasma‐treated materials retain most of their initial crystallinity, while exhibiting somewhat lower surface area and pore volume. XPS and FT‐IR spectroscopy reveal that oxygen plasma induces MIL‐125(Ti)‐NH 2 partial terephthalate decarboxylation and an increase in the Ti‐OH population. Thermogravimetric analyses confirm the generation of structural defects by oxygen plasma and allowed an estimation of the resulting experimental formula of the treated MIL‐125(Ti)‐NH 2 solids. SEM analyses show that oxygen plasma treatment of MIL‐125(Ti)‐NH 2 gradually decreases its particle size. Importantly, diffuse reflectance UV/Vis spectroscopy and valence band measurements demonstrate that oxygen plasma treatment alters the MIL‐125(Ti)‐NH 2 band gap and, more significantly, the alignment of highest occupied and lowest unoccupied crystal orbitals. An optimal oxygen plasma treatment to achieve the highest efficiency in water splitting with or without methanol as sacrificial electron donor under UV/Vis or simulated sunlight was determined. The optimized plasma‐treated MIL‐125(Ti)‐NH 2 photocatalyst acts as a truly heterogeneous photocatalyst and retains most of its initial photoactivity and crystallinity upon reuse.