Methyl orange dye (MO) is one of the azo dyes, which is not only difficult to degrade but also hazardous to human health, therefore, it is necessary to develop an efficient photocatalyst to degrade MO. In this paper, a facile and low-cost elemental doping method was used for the surface modification of Ti₃C₂ MXene, i.e., nitrogen-doped titanium carbide was used as the nitrogen source, and the strategy of combining solvent heat treatment with non-in situ nitrogen doping was used to prepare N-Ti₃C₂ MXene two-dimensional nanomaterials with high catalytic activity. It was found that the catalytic efficiency of N-Ti₃C₂ MXene materials was enhanced and improved compared to the non-doped Ti₃C₂ MXene. In particular, N-Ti₃C₂ 1:8 MXene showed the best photo-catalytic ability, as demonstrated by the fact that the N-Ti₃C₂ 1:8 MXene material successfully degraded 98.73% of MO (20 mg/L) under UV lamp irradiation for 20 min, and its catalytic efficiency was about ten times that of Ti₃C₂ MXene, and the N-Ti₃C₂ photo-catalyst still showed good stability after four cycles. This work shows a simplified method for solvent heat-treating non-in situ nitrogen-doped Ti₃C₂ MXene, and also elaborates on the photo-catalytic mechanism of N-Ti₃C₂ MXene, showing that the high photo-catalytic effect of N-Ti₃C₂ MXene is due to the synergistic effect of its efficient charge transfer and surface-rich moieties. Therefore, N-Ti₃C₂ MXene has a good prospect as a photo-catalyst in the photocatalytic degradation of organic pollutants.

In this study, sugarcane bagasse (SCB) was treated with sodium hydroxide and bleached to separate the non-cellulose components to obtain cellulose (CE) fibres. Cross-linked cellulose–poly(sodium acrylic acid) hydrogel (CE–PAANa) was successfully synthesised via simple free-radical graft-polymerisation to remove heavy metal ions. The structure and morphology of the hydrogel display an open interconnected porous structure on the surface of the hydrogel. Various factors influencing batch adsorption capacity, including pH, contact time, and solution concentration, were investigated. The results showed that the adsorption kinetics were in good agreement with the pseudo-second-order kinetic model and that the adsorption isotherms followed the Langmuir model. The maximum adsorption capacities calculated by the Langmuir model are 106.3, 333.3, and 163.9 mg/g for Cu(II), Pb(II), and Cd(II), respectively. Furthermore, X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectrometry (EDS) results demonstrated that cationic exchange and electrostatic interaction were the main heavy metal ions adsorption mechanisms. These results demonstrate that CE–PAANa graft copolymer sorbents from cellulose-rich SCB can potentially be used for the removal of heavy metal ions.

In recent years, halide perovskite materials have become widely used in solar cells, photovoltaics, and LEDs, as well as photocatalysis. Lead-free perovskite Cs₃Bi₂I₉ has been demonstrated as an effective photocatalyst; however, the fast recombination of the photogenerated carriers hinders further improvements of its photocatalytic activity. In this work, Ti₃C₂ was composited with Cs₃Bi₂I₉ to promote the transfer and separation of photogenerated carriers, and thus the pollutant degradation efficiency was effectively improved. The visible-light photocatalytic reduction of Cs₃Bi₂I₉/Ti₃C₂ on rhodamine B (RhB), methylene blue (MB), and malachite green (MG) was as high as 97.3%, 96%, and 98.8%, respectively, improvements of almost 31.2%, 37.8%, and 37.2% compared to that of sole Cs₃Bi₂I₉. Our study provides a simple way to enhance the photocatalytic activity of lead-free halide perovskites.