Halogen-engineered molecular ferroelectrics for efficient mechanical energy harvesting toward sustainable alkane oxidation

Mechanical energy-driven C(sp³)–H bond activation represents a promising and green strategy for sustainable transformation. However, conventional catalysts are often limited by inefficient mechanical energy input and insufficient piezoelectric voltage output, which significantly restricts their overall catalytic performance. Herein, we report a molecular ferroelectric material, TMCM-GaCl₄ ((CH₃)₃NCH₂Cl-GaCl₄), synthesized via a halogen-substitution strategy. This material exhibits high piezoelectric response (d₃₃), strong piezoelectric voltage output (g₃₃), and excellent acoustic impedance (Z) matching with the reaction medium, demonstrating efficient and sustainable catalytic performance in alkane oxidation. In the light–ultrasound coupled catalytic oxidation of ethylbenzene, TMCM-GaCl₄ achieves a remarkable turnover number (TON) of 3776 ± 368 with 94% selectivity, significantly outperforming conventional inorganic ferroelectric and piezoelectric materials. Experimental and mechanistic studies reveal that the close acoustic impedance match between the material and the solvent enables efficient mechanical energy transfer, inducing lattice vibrations and triggering a pronounced piezoelectric response with high-voltage output. The synergistic interplay among the optical, piezoelectric, and acoustic fields dynamically regulates the adsorption–desorption equilibrium of O₂ and the substrate, reduces the energy barrier for C(sp³)–H bond cleavage, suppresses charge recombination, and accelerates reaction kinetics.

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