Metal-Organic Framework-Based Hetero-Phase Nanostructure Photocatalysts with Molecular-Scale Tunable Energy Levels.

Abstract

As an effective method to modulate the physicochemical properties of materials, crystal phase engineering, especially hetero-phase, plays an important role in developing high-performance photocatalysts. However, it is still a huge challenge but significant to construct porous hetero-phase nanostructures with adjustable band structures. As a kind of unique porous crystalline materials, metal-organic frameworks (MOFs) might be the appropriate candidate, but the MOF-based hetero-phase is rarely reported. Herein, we developed a secondary building unit (SBU) regulating strategy to prepare two crystal phases of Ti-MOFs constructed by titanium and 1,4-dicarboxybenzene, i.e., COK and MIL-125. Besides, COK/MIL-125 hetero-phase was further constructed. In the photocatalytic hydrogen evolution reaction, COK/MIL-125 possessed the highest H2 yield compared to COK and MIL-125, ascribing to the Z-Scheme homojunction at hetero-phase interface. Furthermore, by decorating with amino groups (i.e., NH2-COK/NH2-MIL-125), the light absorbing capacity was broadened to visible-light region, and the visible-light-driven H2 yield was greatly improved. Briefly, the MOF-based hetero-phase possesses periodic channel structures and molecularly adjustable band structures, which is scarce in traditional organic or inorganic materials. As a proof of concept, our work not only highlights the development of MOF-based hetero-phase nanostructures, but also paves a novel avenue for designing high-performance photocatalysts.