Anion Exchange in LaBaInO₃F₂: Structural and Optical Effects of Low-Temperature Topochemical Modification.

Area of Science:

• Materials Science
• Solid-State Chemistry
• Inorganic Chemistry

Background:

• Ruddlesden-Popper (RP) type indium oxyfluorides like LaBaInO₃F₂ are materials with potential applications.
• Controlled modification of these materials, particularly anion exchange, is challenging.
• Stabilizing hydride ions alongside In³⁺ in such structures is notoriously difficult.

Purpose of the Study:

• To investigate the low-temperature topochemical modification of LaBaInO₃F₂ using sodium hydride (NaH).
• To explore phase evolution, anion exchange, and reduction pathways.
• To establish a method for stabilizing hydride ions in indium oxyfluoride frameworks.

Main Methods:

• Low-temperature topochemical modification using varying equivalents of sodium hydride (NaH).
• Combined structural, spectroscopic (XPS, optical), elemental analysis, and density functional theory (DFT) calculations.
• Reoxidation experiments to assess hydride stability.

Main Results:

• Controlled hydride-for-fluoride substitution was achieved, forming mixed-anion oxyfluoride-hydride phases (LaBaInO₃F₂₋ₓHᵧ).
• Moderate NaH content (x ≤ 1) led to hydride incorporation with minimal framework degradation.
• Higher NaH content (x > 1) resulted in secondary phase formation and lattice degradation; subtle indium reduction was observed via XPS.

Conclusions:

• Hydride-based topochemical strategies offer a viable route for controlled anion exchange in RP indium oxyfluorides.
• The study successfully demonstrated a pathway to stabilize hydride ions next to In³⁺.
• Modified materials show potential for photocatalytic and energy applications due to altered optical properties.