Chinese Journal of Structural Chemistry最新文献

Photoluminescence (PL) has been increasingly applied in anticounterfeiting and encryption as counterfeiting becomes more prevalent. However, common luminescent encryption techniques are based on static PL measurements and are easy to counterfeit. In this work, we have developed a thermal vapor deposition (TVD) approach using melem as the unique starting material to synthesize highly homogeneous carbon nitride (CN) thin films featuring unique dynamic PL switching properties. After being irradiated by a white LED, the blue PL intensity of the CN film increases significantly and then fades in darkness, demonstrating excellent recyclability. Experimental results prove that CN films contain cyano groups in the structure, and density functional theory (DFT) calculations indicate that the integration of cyano groups results in traps within the bandgap of CN, suggesting that the dynamic PL switching effect is essentially associated with the fullness of the trap states. We have therefore developed an advanced luminescent device for the secure transmission of encrypted information through controlled illumination. It can be easily read with a portable UV (365 nm) lamp and effectively erased using the white LED, thereby preventing information leakage and showing great potential for many applications.

Photocatalytic CO₂ hydrogenation reactions can produce high-value-added chemicals for industry, solving the environmental problems caused by excessive CO₂ emissions. Iron oxides are commonly used in photocatalytic reactions due to their various structures and suitable band gaps. Nevertheless, the structural evolution and real active components during photocatalytic CO₂ hydrogenation reaction are rarely studied. Herein, a variety of iron oxides including α-Fe₂O₃, γ-Fe₂O₃, Fe₃O₄ and FeO were derived from Prussian blue precursors to investigate the CO₂ hydrogenation performance, structural evolution and active components. Especially, the typical α- and γ-Fe₂O₃ are converted to Fe₃O₄ during the reaction, while Fe/Fe_xO_y remains structurally stable. Meanwhile, it is confirmed that Fe₃O₄ is the main active component for CO production and the formation of hydrocarbons (CH₄ and C₂–C₄) are highly dependent on the Fe/Fe_xO_y heterojunctions. The optimal yields of CO, CH₄ and C₂–C₄ hydrocarbons over the best catalyst (FeFe-550) can achieve 4 mmol g⁻¹ h⁻¹, 350 μmol g⁻¹ h⁻¹ and 150 μmol g⁻¹ h⁻¹, respectively due to their suitable metal/oxide component distribution. This work examines the structural evolution of different iron oxide catalysts in the photocatalytic CO₂ hydrogenation reaction, identifies the active components as well as reveals the relationship between components and the products, and offers valuable insights into the efficient utilization of CO₂.

Given the diversity and complexity of coexisting oil/dyes/heavy metal ions/microorganisms in wastewater and volatile organic compounds (VOCs) in the air, developing separation materials featured in higher separation efficiency and lower energy consumption for oil and water separation, pollutant removal, and anti-fouling is urgently needed, but it remains a major challenge till now. Herein, a multifunctional Ti₃C₂ MXene membrane with unique double pillar support was proposed by liquid phase ultrasonication and vacuum filtration to overcome the above challenge. Introducing cetyl-trimethyl ammonium bromide (CTAB) and calcium chloride/sodium alginate (CaCl₂/SA) to the MXene membrane as crossed double pillars and superhydrophilic surface increases the tolerance and wettability of the membrane. The fabricated doubly pillared MXene (d-Ti₃C₂) membrane exhibits superior oil/water (O/W) separation efficiency (99.76%) with flux (1.284 L m⁻² h⁻¹) for canola oil and organic dye removing efficiency for methyl blue (MB) 99.85%, malachite green (MG) 100%, and methyl violet (MV) 99.72%, respectively, which is 1.05, 1.44, 1.22, and 1.28 fold compared with pre-pillared Ti₃C₂ (p-Ti₃C₂). The superior anti-oil/dye/fouling is attributed to lower oil conglutination, high hydrophily, and antibacterial activity. The versatile MXene membrane also shows distinguished separation of VOCs (η > 99%) from polluted air. The experimental and molecular dynamics (MD) computational simulation results illustrate that the superior separation efficiency of the Ti₃C₂ MXene membrane is ascribed to the unique doubly pillared space channel. This study paves a new road to further research on one step integration strategy for complex O/W separation, wastewater and VOCs removal, and anti-fouling via tuning nano/macro architecture.

Organic radicals feature versatile unpaired electrons key for photoelectronic and biomedical applications but remain difficult to access in stable concentrated forms. We disclose easy generation of stable, concentrated radicals from various alkynyl phenyl motifs, including 1) sulfur-functionalized alkyne-rich organic linkers in crystalline frameworks; 2) the powders of these molecules alone; 3) simple diethynylbenzenes. For Zr-based framework, the generation of radical-rich crystalline framework was achieved by thermal annealing in the range of 300–450 °C. For terminal alkynes, electron paramagnetic resonance signals (EPR, indicative of free radicals) arise after air exposure or mild heating (e.g., 70 °C). Further heating (e.g., 150 °C for 3 h) raises the radical concentrations up to 3.30 mol kg⁻¹. For more stable internal alkynes, transformations into porous radical solids can also be triggered, albeit at higher temperatures (e.g., 250–500 °C). The resulted radical-containing solids are porous, stable to air as well as heat (up to 300–450 °C) and exhibit photothermal conversion and solar-driven water evaporation capacity. The formation of radicals can be ascribed to extensive alkyne cyclizations, forming defects, dangling bonds and the associated radicals stabilized by polycyclic π-systems.