Ligand-hydroxylated UiO-66 for Enhanced Photothermally Catalytic VOCs Oxidation

doi:10.15541/jim20250157

Abstract

Abstract:

The efficient removal of low-concentration volatile organic compounds (VOCs) in indoor and industrial environments remains a significant challenge. Metal-organic frameworks (MOFs) are potential oxidation catalysts due to their superior adsorption enrichment capability for low-concentration VOCs. In this work, hydroxyl-containing ligands were introduced into UiO-66, and the as-synthesized UiO-66-OH catalyst exhibited exceptional photothermal catalytic performance on oxidation of flowing low-concentration VOCs (initial concentrations of 0.075 mg/L for toluene and 0.064 mg/L for benzene, a weight hourly space velocity (WHSV) of 30000 mL/(g∙h)), achieving 97% and 90% conversion of toluene and benzene, respectively, surpassing the reported photothermal catalysts such as metal oxides and noble-metal-loaded catalysts. Such impressive activity is attributed to the synergy of thermal catalysis and photocatalysis. Ligand hydroxylation optimizes the electron structure and the ligand-to-metal charge transfer (LMCT) effect, enhancing light absorption, improving electron-hole separation efficiency and photothermal properties of UiO-66. Hydroxyl introduction promotes the formation of oxygen vacancies, facilitating oxygen adsorption/activation to sustain lattice oxygen (O_latt) and generate superoxide radical (∙O₂^-), which are the dominant reactive species in VOCs oxidation. This work not only presents the potential of MOFs as efficient photothermal catalysts for the oxidation of low-concentration VOCs but also shows prospects on facile modulation of electron structure by ligand engineering to enhance the photothermal properties of MOFs.

Key words: volatile organic compound, low concentration, metal-organic framework, photothermal catalysis, ligand-to-metal charge transfer effect

CLC Number:

TQ134

CHEN Xiaochen, WANG Yang, YANG Bin, WANG Min, A Bohan, WANG Man, ZHANG Lingxia. Ligand-hydroxylated UiO-66 for Enhanced Photothermally Catalytic VOCs Oxidation[J]. Journal of Inorganic Materials, 2026, 41(5): 663-672.

Figures/Tables 15

Fig. 1 (a) Schematic diagram of the synthesis procedure, (b) XRD patterns and (c) FT-IR spectra of UiO-66 and UiO-66-X

Fig. 2 (a, b) Photothermal catalytic performance of UiO-66-X and UiO-66 for oxidation of (a) toluene and (b) benzene, and (c, d) cycle stability of UiO-66-OH for photothermal catalytic oxidation of (c) toluene and (d) benzene

Fig. 3 (a) Surface temperature of the catalysts, (b) schematic band structure, (c) O1s XPS spectra, and (d) active species trapping experiments of UiO-66-OH

Fig. 4 In-situ FT-IR spectra of UiO-66-OH for oxidation of toluene under different successive conditions (a) In dark without O2; (b) In dark with O2; (c, d) With O2 and irradiation

Fig. 5 In-situ FT-IR spectra of UiO-66-OH for oxidation of benzene under different successive conditions (a) In dark without O2; (b) In dark with O2; (c, d) With O2 and irradiation

Table S1 Hydrothermal conditions for the synthesis of UiO-66 and UiO-66-X catalysts

Sample	Temperature/℃	Time/h
UiO-66	120	24
UiO-66-NDC	120	24
UiO-66-NO₂	120	24
UiO-66-NH₂	120	12
UiO-66-OH	80	12

Table S2 Performance comparison of relevant catalysts on benzene and toluene oxidation

Catalyst	VOC	Concentration/(mg∙L^-1)	Catalyst amount/mg	Light intensity/(mW∙cm^-2)	Conversion/%
Pt/TiO₂^[S2]	Benzene	0.96	100	300	84.5
Pt/g-C₃N₄^[S3]	Benzene	0.96	150	500	95
This work	Benzene	0.064	100	300	90
MnO_x-TiO₂^[S4]	Toluene	0.02	500	-	72
TiO₂-UiO-66-NH₂^[9]	Toluene	0.094	100	50	73
Pt/MnO_x^[S5]	Toluene	0.75	100	200	90
This work	Toluene	0.075	100	300	97

Fig. S1 FT-IR spectrum of UiO-66-NH2 in the range of 2000-4000 cm-1

Fig. S2 (a, b) SEM images and (c) XRD patterns of UiO-66-OH (a) before and (b) after five catalytic cycles

Fig. S3 N2 adsorption-desorption isotherms at 77 K with inset showing pore-size distributions of UiO-66 and UiO-66-OH

Fig. S4 (a) UV-Vis absorption spectra; (b) Tauc plots; (c, d) Mott-Schottky plots of (c) UiO-66 and (d) UiO-66-OH

Fig. S5 (a) PL spectra, (b) photocurrent response spectra and (c) Nyquist plots of UiO-66 and UiO-66-OH

Fig. S6 (a, b) Zr3d XPS spectra of (a) UiO-66 and (b) UiO-66-OH, (c) EPR spectra of UiO-66 and UiO-66-OH, and(d) comparison of toluene and benzene conversion by photothermal catalysis and thermal catalysis

Fig. S7 In-situ FT-IR spectra of UiO-66 for oxidation of (a) toluene and (b) benzene under O2 and irradiation conditions

Fig. S8 Possible oxidation reaction pathways of toluene and benzene on UiO-66-OH

References 33

[1]	HE C, CHENG J, ZHANG X, et al. Recent advances in the catalytic oxidation of volatile organic compounds: a review based on pollutant sorts and sources. Chemical Reviews, 2019, 119(7): 4471. DOI PMID
[2]	MARINO E, CARUSO M, CAMPAGNA D, et al. Impact of air quality on lung health: myth or reality? Therapeutic Advances in Chronic Disease, 2015, 6(5): 286. DOI PMID
[3]	HUANG H B, XU Y, FENG Q Y, et al. Low temperature catalytic oxidation of volatile organic compounds: a review. Catalysis Science & Technology, 2015, 5(5): 2649.
[4]	ELIMIAN E A, ZHANG M, SUN Y, et al. Harnessing solar energy towards synergistic photothermal catalytic oxidation of volatile organic compounds. Solar RRL, 2023, 7(14): 2300238. DOI URL
[5]	YANG Y, ZHAO S H, CUI L F, et al. Recent advancement and future challenges of photothermal catalysis for VOCs elimination: from catalyst design to applications. Green Energy & Environment, 2023, 8(3): 654.
[6]	MA X L, WANG W L, SUN C G, et al. Adsorption performance and kinetic study of hierarchical porous Fe-based MOFs for toluene removal. Science of the Total Environment, 2021, 793: 148622. DOI URL
[7]	CHEN R F, YAO Z X, HAN N, et al. Insights into the adsorption of VOCs on a cobalt-adeninate metal-organic framework (bio-MOF-11). ACS Omega, 2020, 5(25): 15402. DOI PMID
[8]	LV S W, LIU J M, LI C Y, et al. Two novel MOFs@COFs hybrid-based photocatalytic platforms coupling with sulfate radical-involved advanced oxidation processes for enhanced degradation of bisphenol A. Chemosphere, 2020, 243: 125378. DOI URL
[9]	ZHANG J H, HU Y, QIN J X, et al. TiO₂-UiO-66-NH₂ nanocomposites as efficient photocatalysts for the oxidation of VOCs. Chemical Engineering Journal, 2020, 385: 123814. DOI URL
[10]	WU X P, GAGLIARDI L, TRUHLAR D G. Cerium metal-organic framework for photocatalysis. Journal of the American Chemical Society, 2018, 140(25): 7904. DOI URL
[11]	HEU R, ATEIA M, YOSHIMURA C. Photocatalytic nanofiltration membrane using Zr-MOF/GO nanocomposite with high-flux and anti-fouling properties. Catalysts, 2020, 10(6): 711. DOI URL
[12]	KIM H G, CHOI K, LEE K, et al. Controlling the structural robustness of zirconium-based metal organic frameworks for efficient adsorption on tetracycline antibiotics. Water, 2021, 13(13): 1869. DOI URL
[13]	NAIK T S S K, SINGH S, PAVITHRA N, et al. Advanced experimental techniques for the sensitive detection of a toxic bisphenol A using UiO-66-NDC/GO-based electrochemical sensor. Chemosphere, 2023, 311: 137104. DOI URL
[14]	MA Y L, LI A R, WANG Z H, et al. Preparation of UiO-66-type adsorbents for the separation of SO₂ from flue gas. Adsorption, 2024, 30(3): 377. DOI
[15]	LUCATERO E, BASHIRI R, SO M C. Synthesis, characterization, and evaluation of metal-organic frameworks for oxidative desulfurization: an integrated experiment. Journal of Chemical Education, 2024, 101(8): 3428. DOI URL
[16]	YOU X Q, LI Y, MO H R, et al. Theoretical studies on Lennard-Jones parameters of benzene and polycyclic aromatic hydrocarbons. Faraday Discussions, 2022, 238: 103. DOI PMID
[17]	ZHAO Y, WANG Y, WANG X Y, et al. Recent progress of photothermal therapy based on conjugated nanomaterials in combating microbial infections. Nanomaterials, 2023, 13(15): 2269. DOI URL
[18]	MOGHADDAM Z S, KAYKHAII M, KHAJEH M, et al. Synthesis of UiO-66-OH zirconium metal-organic framework and its application for selective extraction and trace determination of thorium in water samples by spectrophotometry. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2018, 194: 76. DOI URL
[19]	NGUYEN V H, PHAM A L H, NGUYEN V H, et al. Facile synthesis of bismuth(III) based metal-organic framework with difference ligands using microwave irradiation method. Chemical Engineering Research and Design, 2022, 177: 321. DOI URL
[20]	WRIGHT S, BARKLIE R C. EPR characterization of defects in monoclinic powders of ZrO₂ and HfO₂. Materials Science in Semiconductor Processing, 2006, 9(6): 892. DOI URL
[21]	ZHANG Y T, CHENG C, ZHOU Z H, et al. Surface hydroxylation during water splitting promotes the photoactivity of BiVO₄(010) surface by suppressing polaron-mediated charge recombination. 2023, 14(40): 9096.
[22]	WU H, CHUA Y S, KRUNGLEVICIUTE V, et al. Unusual and highly tunable missing-linker defects in zirconium metal-organic framework UiO-66 and their important effects on gas adsorption. Journal of the American Chemical Society, 2013, 135(28): 10525. DOI PMID
[23]	BAKRADZE G, JEURGENS L P H, MITTEMEIJER E J. Valence-band and chemical-state analyses of Zr and O in thermally grown thin zirconium-oxide films: an XPS study. The Journal of Physical Chemistry C, 2011, 115(40): 19841. DOI URL
[24]	CHI M Y, SUN X N, SUJAN A, et al. A quantitative XPS examination of UV induced surface modification of TiO₂ sorbents for the increased saturation capacity of sulfur heterocycles. Fuel, 2019, 238: 454. DOI URL
[25]	JIANG Y, NING H Y, TIAN C G, et al. Single-crystal TiO₂ nanorods assembly for efficient and stable cocatalyst-free photocatalytic hydrogen evolution. Applied Catalysis B: Environmental, 2018, 229: 1. DOI URL
[26]	LIU L Z, HUANG H W, CHEN F, et al. Cooperation of oxygen vacancies and 2D ultrathin structure promoting CO₂ photoreduction performance of Bi₄Ti₃O₁₂. Science Bulletin, 2020, 65(11): 934. DOI URL
[27]	IBRAHIM D A H, HAIKAL D R R, ELDIN R S, et al. The role of free-radical pathway in catalytic dye degradation by hydrogen peroxide on the Zr-based UiO-66-NH₂ MOF. ChemistrySelect, 2021, 6(42): 11675. DOI URL
[28]	MERKEL P B, LUO P, DINNOCENZO J P, et al. Accurate oxidation potentials of benzene and biphenyl derivatives via electron- transfer equilibria and transient kinetics. 2009, 74(15): 5163.
[29]	LIN H X, LONG J L, GU Q, et al. In situ IR study of surface hydroxyl species of dehydrated TiO₂: towards understanding pivotal surface processes of TiO₂ photocatalytic oxidation of toluene. Physical Chemistry Chemical Physics, 2012, 14(26): 9468. DOI URL
[30]	WANG F Z, LI W J, GU S N, et al. Fabrication of FeWO₄@ZnWO₄/ZnO heterojunction photocatalyst: synergistic effect of ZnWO₄/ZnO and FeWO₄@ZnWO₄/ZnO heterojunction structure on the enhancement of visible-light photocatalytic activity. ACS Sustainable Chemistry & Engineering, 2016, 4(12): 6288.
[31]	MO S P, LI J, LIAO R Q, et al. Unraveling the decisive role of surface CeO₂ nanoparticles in the Pt-CeO₂/MnO₂ hetero-catalysts for boosting toluene oxidation: synergistic effect of surface decorated and intrinsic O-vacancies. Chemical Engineering Journal, 2021, 418: 129399. DOI URL
[32]	MO S P, ZHANG Q, LI J Q, et al. Highly efficient mesoporous MnO₂ catalysts for the total toluene oxidation: oxygen-vacancy defect engineering and involved intermediates using in situ DRIFTS. Applied Catalysis B: Environmental, 2020, 264: 118464. DOI URL
[33]	CHEN L C, CHEN P, WANG H, et al. Surface lattice oxygen activation on Sr₂Sb₂O₇ enhances the photocatalytic mineralization of toluene: from reactant activation, intermediate conversion to product desorption. ACS Applied Materials & Interfaces, 2021, 13(4): 5153.