Ligand Bridged Mxene/Metal Organic Frameworks Heterojunctions for Efficient Photocatalytic Ammonia Synthesis

The efficient transfer of charge carriers between interfaces of components is crucial for enhancing the performance of heterogeneous photocatalysts. Herein, ligand-bridged MXene/MIL-125(Ti) was successfully achieved by employing a unique ligand pre-coupling strategy, wherein the terminal oxygen group of Ti3C2Ox is coupled to the carboxyl group of the ligands of MIL-125(Ti). This ligand-bridge effectively reduces the interface charge transfer resistance, enhancing the separation efficiency of charge carriers. Raman, XPS and electron location function (ELF) calculations confirm the formation of coordination bonds between the Ti3C2Ox and the ligands. Kelvin probe force microscopy and charge density difference analysis reveal that an electronic unidirectional transport channel from MIL-125(Ti) to Ti3C2Ox is established through the ligand-bridge. Consequently, the Ti3C2Ox/MIL-125(Ti) exhibits an excellent ammonia evolution rate of 103.02 μmol·gcat-1·h-1. The strategy is also demonstrated to be efficient for accelerating the photogenerated carriers separation of five other MOFs, showing good universality in constructing ligand-bridged MXene/MOFs heterojunctions.