Modulation of interface structure on titanium-based metal-organic frameworks heterojunctions for boosting photocatalytic carbon dioxide reduction.

Abstract

Rational regulation of interface structure in photocatalysts is a promising strategy to improve the photocatalytic performance of carbon dioxide (CO₂) reduction. However, it remains a challenge to modulate the interface structure of multi-component heterojunctions. Herein, a strategy integrating heterojunction with facet engineering is developed to modulate the interface structure of metal-organic frameworks (MOF)-based heterojunctions. A series of core-shell UiO-66 (Zr-MOF)-loaded MIL-125 (Ti-MOF) heterojunctions with exposed specific facets were prepared to enhance the separation efficiency of photogenerated electrons-holes in CO₂ photoreduction. Impressively, MIL-125_to@UiO-66 with exposed {1 1 1} facet exhibits an excellent CO production rate (56.4 μmol g^-1 h^-1) and selectivity (99 %) under visible light irradiation without any photosensitizers/sacrificial agents, being 1.4 and 11.3 times higher than individual MIL-125_to and UiO-66, respectively. The type-II heterojunction significantly enhances the separation of photogenerated electrons-holes in physical space. The photogenerated electrons migrate from Zr in UiO-66 to Ti in MIL-125_to, promoting a spatial synergy between CO₂ reduction on MIL-125_to and H₂O oxidation on UiO-66. Compared with MIL-125_rd@UiO-66 with exposed {1 1 0} facet and MIL-125_ds@UiO-66 with exposed {0 0 1} facet, MIL-125_to@UiO-66 with exposed {1 1 1} facet improves the exposure of surface-active Ti sites, thereby enhancing the adsorption/activation of CO₂ to generate the *COOH intermediate. This work provides an effective strategy for designing MOF-based heterojunction photocatalysts to improve photocatalytic performance.