Mxene-modulated dual-heterojunction generation on a metal-organic framework (MOF) via surface constitution reconstruction for enhanced photocatalytic activity

Regulation of photocarriers separation and transport is an important factor influencing photocatalytic efficiency. Herein, Ti3C2-modulated MIL-125-NH2-based nanohybrids with dual-heterojunctions was synthetized by a one-step solvothermal strategy for enhanced photocatalysis activity. The Ti3C2 nanosheets played a significant role in determining the morphology, constituent and photoelectricity property of MIL-125-NH2-based nanohybrids. At an increasing level of Ti3C2 in the precursor solution, there was an evolution of TiO2 formation on the surface of NH2-MIL-125(Ti), along with the partial loss of organic linker. Meanwhile, the formed TiO2 undergone a morphology transformation from 2D nanosheets to 3D nanoparticles. The optimized NH2-MIL-125(Ti)(TiO2)/Ti3C2 nanohybrids yielded 1.65 times higher H2O2 production rate and 11.5 times higher tetracycline hydrochloride (TC-HCl) degradation efficiency than that of the pristine MIL-125-NH2 under visible light irradiation (lambda > 420 nm). As confirmed by some characterization techniques, the improved photocatalytic activities were dominantly ascribed to the dual-heterojunction in NH2-MIL-125(Ti)(TiO2)/Ti3C2, which not only enhanced the carrier density, but also remarkably accelerated the interfacial charge separation, as well as transfer. The radical trapping experiments and ESR spectra assured the center dot OH and h(+) were the major reactive species in photocatalytic activities. Additionally, the TC-HCl degradation pathway was proposed by liquid chromatography-mass spectrometry (LC-MS) and the photocatalytic mechanism corresponding to the enhanced photocatalytic H2O2 production and TC-HCl degradation by MT5 was speculated. The construction of MIL-125-NH2(TiO2)/Ti3C2 nanohybrid provides a promising hybridization strategy on MOFs-based composites with controllable adjustment, morphology design, and property optimization for addressing issues on the environment and sustainable energy.