MOF-derived phase-selective synthesis of ln2O3 with appropriate surface atomic arrangement for CO2 photoreduction

Crystal phase engineering emerges as a powerful strategy to enhance photocatalytic activity, yet controlled phase-selective synthesis and phase-dependent performance understanding remain challenging. In this study, we introduce a method for synthesizing phase-engineered In 2 O 3 via the pyrolysis of metal–organic frameworks (MOFs). We demonstrate that the functional group and pyrolysis temperatures of MOFs are critical for phase-selective synthesis. Specifically, pyrolysis of MIL-68(ln)–NH 2 at optimal temperatures yields In 2 O 3 with rhombohedral (rh-In 2 O 3 ), cubic (c-In 2 O 3 ), and rhombohedral/cubic heterophase (rh/c-In 2 O 3 ) structures. The photocatalytic CO 2 reduction tests reveal that c-In 2 O 3 outperforms rh-In 2 O 3 and rh/c-In 2 O 3 , achieving a CO production rate of 29.19 μmol g -1 h −1 with 94.47 % selectivity. Spectroscopic and theoretical analyses show that c-In 2 O 3 has superior charge transfer efficiency and lower reaction energy barriers, particularly for the rate-determining *CO intermediate, which exhibits a lower Gibbs free energy on its surface. This work provides a significant advancement in optimizing photocatalytic CO 2 reduction efficiency through precise phase engineering, underscoring the vital role of phase control in enhancing catalytic performance.