Carbon-Cloth-Templated Oxygen Vacancies Enable Direct Benzene Ring-Opening for Cleaner Photocatalytic VOC Abatement.

Abstract

Gaseous benzene, a Group-1 carcinogenic volatile organic compound (VOC) widely released from petrochemical and solvent-based industries, poses a persistent obstacle to cleaner industrial production owing to the leakage of toxic aromatic intermediates, such as phenol and p-benzoquinone, during incomplete photocatalytic oxidation. Conventional MnO2-based photocatalysts further suffer from weak substrate adsorption and sluggish charge separation, resulting in high energy penalties and secondary pollution. Herein, a carbon-cloth (CC)-induced defect-engineering strategy was developed to fabricate an oxygen-vacancy-enriched MnO2 monolithic photocatalyst (Vo-MnO2@CC) for low-energy, by-product-suppressed photocatalytic benzene oxidation (PBO). Density functional theory (DFT) calculations combined with EPR, XPS, COHP, and in-situ DRIFT evidence demonstrate that electron donation from CC weakens surface Mn-O bonds and spontaneously generates abundant, thermally stable surface oxygen vacancies (Vo) without chemical reductants. The Vo-modulated surface up-shifts the Mn d-band center from 2.62 to 3.77 eV, strengthens the chemisorption of benzene (Eads = -2.31 eV), H2O, and O2, and accelerates the generation of ·OH and ·O2- radicals. Concurrently, covalent C-O-Mn linkages establish a directional electron-transport channel that prolongs carrier lifetime from 2.85 to 10.39 ns and suppresses electron-hole recombination. Critically, GC-MS and DFT analyses reveal that Vo-MnO2@CC reverses the conventional ring-opening energy landscape, lowering the activation barrier of direct benzene ring-opening (1.38 eV) below those of phenol (1.60 eV) and p-benzoquinone (1.47 eV), thereby unlocking a "direct ring-opening pathway" that bypasses toxic aromatic intermediates. Consequently, Vo-MnO2@CC achieves 99.13% benzene conversion with 96.93% CO2 mineralization within 30 min, retains 95.09% activity over 15 h of fixed-bed operation and 90.32% benzene conversion over 60 h of continuous-flow operation, and shows broad-spectrum efficacy toward formaldehyde, acetaldehyde, and toluene. This work offers mechanistic insight into vacancy-mediated thermodynamic regulation and a scalable, binder-free, low-energy photocatalyst platform aligned with cleaner-production goals for the sustainable abatement of recalcitrant aromatic VOCs.

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