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A highly nitrogen-deficient g-C3N4 (AH-CN) nanosheet material was successfully prepared via an acetaldehyde-assisted hydrothermal route. The as-prepared AH-CN material was analyzed by X-ray powder diffraction (XRD), N2 physical adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), Fourier transform infrared (FT-IR) spectroscopy, UV–vis diffuse reflectance spectroscopy (UV-Vis DRS), elemental analysis (EA), electron paramagnetic resonance (EPR) and photoelectric tests. Compared with H-CN (g-C3N4 treated hydrothermally without acetaldehyde), a large number of nitrogen vacancies were produced over AH-CN (g-C3N4 treated under acetaldehyde-assisted hydrothermal conditions). The bandgap of AH-CN decreases and its light absorption was largely improved in UV and visible light regions. Moreover, the as-prepared material possesses a low recombination rate of photogenerated carriers and a relatively negative conduction band potential over AH-CN, which contributes to its strong photocatalytic reduction ability. Under simulated sunlight illumination, the photocatalytic performance for H2O2 production and Cr(VI) reduction of the AH-CN material was evaluated. The highest H2O2 yield of 670 μM was obtained over 50AH-CN, which was 2.6 times that of g-CN. In the removal of Cr(VI) via reduction, the removal rate of Cr(VI) over 50AH-CN reaches 56% which is about 5.6 times that of g-CN. [ABSTRACT FROM AUTHOR]

The progress of two-dimensional (2D) MXene-derived QDs (MQDs) is in the early stages, but the materials have aroused great interest due to their high electrical conductivity, abundant active catalytic sites, easily tunable structure, satisfactory dispersibility, remarkable optical properties, good biocompatibility, manifold functionalizations, and so on. However, up to now, there is still no review paper on MQDs. Herein, the research advances of MQDs, including their synthetic routes (top-down and bottom-up methods), properties (structural, electronic, optical and magnetic properties), functionalizations (surface modifications, heteroatom doping and the construction of composites) and applications (sensing, biomedical, catalysis, energy storage and optoelectronic devices etc.), are critically highlighted, and the future prospects and challenges of MQDs are discussed. This review will serve as a one-stop point for comprehending the most advanced developments of MQDs, and will hopefully enlighten researchers to employ MQDs for satisfying the growing requirements of the diverse applications. [ABSTRACT FROM AUTHOR]

Solar energy is a clean and sustainable energy source. Natural photosynthesis has existed for millions of years, which can convert solar energy into chemical energy needed by living things. Inspired by natural photosynthesis, scientists have developed a series of artificial photosynthetic systems that can use solar energy efficiently for humans. Conjugated microporous polymers (CMPs) are a new class of materials that can be used in artificial photosynthetic systems. This review illustrates the light-harvesting capability and the energy transfer phenomena within the supramolecular structure of CMPs to provide guidelines for the rational design of these polymers with excellent photocatalytic properties and systematically discusses the applications of these materials in the field of photocatalysis including photocatalytic water splitting, CO2 reduction, organic conversion, environmental remediation, and medical health. Finally, this review points out the major challenges in this topic and suggests the next feasible development direction. [ABSTRACT FROM AUTHOR]

Metal-free black phosphorus (BP) nanosheets have emerged as a promising photocatalyst. Herein, early transition-metal carbide and nitride (MXene) decorated BP (Ti3C2Tx/TiO2–BP) nanohybrids were constructed by a hydrothermal method, in which TiO2 was produced in the hydrothermal process. The optimized Ti3C2Tx/TiO2–BP nanohybrids exhibited a higher visible-light photodegradation efficiency of rhodamine B (99.09%) and tetracycline hydrochloride (92.70%) pollutants than that of pristine BP (12.75% and 9.35%, respectively). Diverse characterization techniques and density functional theory calculations have revealed that such enhanced photocatalytic performance was due to the synergistic effect of BP and Ti3C2Tx/TiO2, which could markedly improve the stability of BP, increase visible light absorption, prolong the photoexcited electron lifetime, accelerate the photoinduced electron transfer and hinder the electron–hole (e−–h+) pair recombination. Meanwhile, the mechanism analysis indicated that ˙O2− radicals played a leading role in the photocatalytic process. This study will motivate great interest in using 2D MXenes as co-catalysts to enhance the activity of BP for its applications. [ABSTRACT FROM AUTHOR]