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 (λ > 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 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.