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Enhanced Charge Separation and Visible-Light Utilization in La-Doped MIL-100(Fe) for Efficient Cr(VI) Photoreduction

Year: 2026

Type: article

Abstract: Lanthanum-doped MIL-100(Fe) (MIL-100(Fe0.99/La0.01)) was successfully synthesized through a facile and environmentally friendly room-temperature stirring method to enhance charge separation and visible-light utilization for Cr(VI) photoreduction. Structural characterization using XRD, FT-IR, SEM-EDS, BET, and UV–Vis reflectance spectroscopy confirmed the formation of a highly crystalline MIL-100(Fe) framework with uniform octahedral morphology, hierarchical micro–mesoporous structure, and effective La incorporation into the framework. The La3+ dopant modified the local electronic structure by introducing electron-trapping sites, suppressing electron–hole recombination, and extending visible-light absorption up to 700 nm. The La-doped sample had a narrower optical band gap (2.93 eV) than the pure MIL-100(Fe), which means it could collect light better. Photocatalytic experiments under visible-light irradiation demonstrated that MIL-100(Fe0.99/La0.01) achieved superior Cr(VI) reduction efficiency (88.35%) within 35 min at pH = 5, outperforming undoped MIL-100(Fe) (60.04%) under identical conditions. Enhanced electrostatic interaction between positively charged catalyst surfaces and negatively charged Cr(VI) species (HCrO4–, Cr2O72–) facilitates interfacial charge transfer and is responsible for the best performance at mildly acidic pH. Active-species trapping experiments revealed that hydroxyl radicals (•OH) were the dominant reactive species, with superoxide radicals (•O2–) and photogenerated holes (h+) contributing minor roles. Kinetic analysis followed a pseudo-first-order model (k1 = 0.088 min–1, R2 = 0.9965), confirming efficient reaction dynamics. Improved light absorption, hierarchical porosity that facilitates mass transport, and effective charge separation through La-induced defect states all work together to produce the increased photocatalytic activity of La-doped MIL-100(Fe). This study not only establishes a sustainable, low-energy synthesis route for rare-earth-modified MOFs but also offers useful information regarding the design of visible-light-responsive mixed-metal frameworks for environmental remediation. The findings highlight La-doped MIL-100(Fe) as a promising photocatalyst for Cr(VI) detoxification and broader applications in solar-driven wastewater treatment.

Source: ACS Omega

DOI: 10.1021/acsomega.5c12227

Authors: Minh Hue Thi Dang, Linh Phuong Bui, Chinh Dang Huynh

Institutions: Trường Đại học Khoa học và Công nghệ Hà Nội, Hanoi University of Science and Technology

Language: English

Topic: Advanced Photocatalysis Techniques

Subfield: Renewable Energy, Sustainability and the Environment

Field: Energy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,935

Funder: Trường Đại học Bách Khoa Hà Nội