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. 2023 Jan 4:10:1102920.
doi: 10.3389/fchem.2022.1102920. eCollection 2022.

In-situ construction of Zr-based metal-organic framework core-shell heterostructure for photocatalytic degradation of organic pollutants

Yasmeen S Abdel Aziz  1 , Moustafa M S Sanad  2 , Reda M Abdelhameed  3 , Ayman H Zaki  4   5
Affiliations

In-situ construction of Zr-based metal-organic framework core-shell heterostructure for photocatalytic degradation of organic pollutants

Yasmeen S Abdel Aziz et al. Front Chem. .

Abstract

Photocatalysis is an eco-friendly promising approach to the degradation of textile dyes. The majority of reported studies involved remediation of dyes with an initial concentration ≤50 mg/L, which was away from the existing values in textile wastewater. Herein, a simple solvothermal route was utilized to synthesize CoFe2O4@UiO-66 core-shell heterojunction photocatalyst for the first time. The photocatalytic performance of the as-synthesized catalysts was assessed through the photodegradation of methylene blue (MB) and methyl orange (MO) dyes at an initial concentration (100 mg/L). Under simulated solar irradiation, improved photocatalytic performance was accomplished by as-obtained CoFe2O4@UiO-66 heterojunction compared to bare UiO-66 and CoFe2O4. The overall removal efficiency of dyes (100 mg/L) over CoFe2O4@UiO-66 (50 mg/L) reached >60% within 180 min. The optical and photoelectrochemical measurements showed an enhanced visible light absorption capacity as well as effective interfacial charge separation and transfer over CoFe2O4@UiO-66, emphasizing the successful construction of heterojunction. The degradation mechanism was further explored, which revealed the contribution of holes (h+), superoxide (•O2 -), and hydroxyl (•OH) radicals in the degradation process, however, h+ were the predominant reactive species. This work might open up new insights for designing MOF-based core-shell heterostructured photocatalysts for the remediation of industrial organic pollutants.

Keywords: MOFs; core-shell; dyes; ferrite; photocatalysis; visible light.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

SCHEME 1
SCHEME 1
Schematic representation of CoFe2O4@UiO-66 composite preparation.
FIGURE 1
FIGURE 1
XRD patterns of UiO-66, CoFe2O4, and CoFe2O4@UiO-66 composite.
FIGURE 2
FIGURE 2
FTIR spectra of UiO-66, CoFe2O4, and CoFe2O4@UiO-66 composite.
FIGURE 3
FIGURE 3
FESEM images of UiO-66 (A) and CoFe2O4@UiO-66 composite (B); UiO-66 particle size distribution of UiO-66 (C) and CoFe2O4@UiO-66 composite (D).
FIGURE 4
FIGURE 4
TEM images (A,B) and SAED pattern (C) of CoFe2O4@UiO-66 composite.
FIGURE 5
FIGURE 5
SEM-EDS elemental mapping of CoFe2O4@UiO-66 composite.
FIGURE 6
FIGURE 6
XPS spectra of CoFe2O4@UiO-66 composite: survey scan (A), C 1s (B), O 1s (C), Zr 3 days (D), Co 2p (E), and Fe 2p (F).
FIGURE 7
FIGURE 7
N2 adsorption-desorption isotherms (A), and pore size distribution curves (B) of UiO-66 and CoFe2O4@UiO-66 composite.
FIGURE 8
FIGURE 8
Thermal analysis of UiO-66, CoFe2O4, and CoFe2O4@UiO-66 composite, inset: the corresponding derivative thermogravimetric (DTG) plots.
FIGURE 9
FIGURE 9
UV-vis DRS spectra (A), bandgap (Eg) plots (B–D) of the as-synthesized samples.
FIGURE 10
FIGURE 10
PL emission spectra (A), EIS Nyquist (B), and LSV curves (C) of UiO-66, CoFe2O4 and CoFe2O4@UiO-66 composite.
FIGURE 11
FIGURE 11
Adsorption and photodegradation performance of as-synthesized photocatalysts for removal of MB (A,C) and MO (B,D) dyes.
FIGURE 12
FIGURE 12
The photodegradation efficiency of as-synthesized photocatalysts (A), UV-Vis absorption spectra for degradation of MB (B) and MO (C) dyes over CoFe2O4@UiO-66.
FIGURE 13
FIGURE 13
The effect of different quenchers on the photocatalytic activity of CoFe2O4@UiO-66 for degradation of MB and MO dyes.
FIGURE 14
FIGURE 14
Mott-Schottky plots of UiO-66 (A) and CoFe2O4 (B).
FIGURE 15
FIGURE 15
A proposed photocatalytic mechanism for dye degradation over CoFe2O4@UiO-66 heterojunction under simulative solar irradiation.
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