Supramolecular Assembly of Hydrogen-Bonded Organic Frameworks with Carbon Dots: Realizing Ultralong Aqueous Room-Temperature Phosphorescence for Anticounterfeiting.

Room-temperature phosphorescent carbon dots (RTP-CDs) have received increasing attention due to their excellent optical properties and potential applications. Nevertheless, the realization of RTP-CDs in aqueous solutions remains a considerable challenge due to the water-molecule- and oxygen-induced deactivation of the triplet excitons, which leads to phosphorescence quenching. In this study, ultralong phosphorescence in water was achieved by in situ self-assembly of CDs encapsulated in a rigid hydrogen-bonded organic framework (HOF). The phosphorescence lifetime reaches an impressive 956.96 ms and exhibits long-lasting optical and structural stability in water for more than 90 days. The composite material not only has ultralong luminescence life and excellent luminescence stability but also has two-color phosphorescence emission, as well as excellent antiphotobleaching and phosphorescence stability in aqueous solution, which can solve the current problem that RTP is easily burst out by water and moisture. In addition, this study introduced a fluorescent dye based on the triplet-singlet Förster resonance energy transfer system (TS-FRET) to fine-tune the afterglow properties. This work will inspire the design of RTP systems with dual phosphor light sources and provide new strategies for the development of smart RTP materials in water.

One-dimensional coordinated polymers of tetraphenylethene pyridine and copper-iodide for fluorescence detection of nitroaromatic explosives.

The spatial arrangement of molecules plays a crucial role in determining the macroscopic properties of functional materials. Coordinated polymers (CPs) formed by self-assembly of organic isomeric ligands and metals offer unique performance characteristics. In this study, we present the investigation of a one-dimensional CP, named CIT-E, composed of tetraphenylethene pyridine derivative (TPE-2by-2-E) ligands and copper iodide. The resulting CP exhibits a one-dimensional bead chain structure with exceptional thermal and chemical stability. By leveraging the competitive absorption between CIT-E and the explosive analog 2,4-dinitroaniline, we achieve detection of the explosive through changes in the absorption intensity of the excitation light source and subsequent fluorescence response. The CP demonstrates high selectivity and anti-interference ability in detecting 2,4-dinitroaniline in aqueous solution, with a detection linear range of 0.1 to 300 µM and a detection limit of 0.05 µM, surpassing the national third-level emission standard. These findings highlight the potential of CP CIT-E as a promising material for the detection of explosive nitroaromatic compounds.

LDH-assisted growth of FeCo bimetal-MOF nanorods for electrocatalytic oxygen evolution.

Metal-organic frameworks (MOFs) have emerged as alternative OER catalysts due to their easy regulation, such as in situ self-reconstruction from MOFs to metal hydroxides through alkaline hydrolysis. Herein, we demonstrate a facile strategy for the in situ transformation of FeCo layered double hydroxide (FeCo-LDH) nanosheets into 1D spindle-shaped FeCo-MOFs for efficient OER. An optimized electrode of FeCo-MOF on a nickel foam (NF) was achieved by adjusting the addition of organic ligands and the reaction time in the hydrothermal reaction. Based on the unique 1D nanostructure and the cation regulation, the obtained FeCo-MOF exhibits a good catalytic performance toward the OER with a low overpotential of 475 mV at 100 mA cm-2, a small Tafel slope of 121.8 mV dec-1, and high long-term durability. This study provides a facile strategy for preparing bimetal-MOFs as catalysts for efficient OER.

Pyridinic nitrogen enables dechlorination of trichloroethylene to acetylene by green rust: Performance, mechanism and applications.

Carbonous materials were found to catalyze the dechlorination of trichloroethylene (TCE) by green rust (GR), but the catalytic mechanism was not fully understood. We have developed a facile ball milling method to synthesize N-doped graphene (NG) with various N species, catalyzing fast dechlorination of TCE to acetylene by GR with the highest acetylene production rate of ~0.1 d-1. The adsorption of TCE onto NG is mainly derived from the graphene region of NG, and high pyridinic N is essential for the enhanced TCE reduction by GR. Oxygen species did not enhance the TCE reduction in GR/NG system. High dechlorination rates are correlated to a high amount of defect in NG and a high electron conductivity of NG. Pyridinic N has the highest adsorption energy for TCE among all the N species, which leads to the highest catalytic performance. High electrochemically active surface area resulted from the high content of pyridinic N facilitate the NG-catalyzed dechlorination. The acetylene production rate in real groundwater is still around one-third of that in ultrapure water. This work not only reveals the catalytic mechanism of NG-catalyzed dechlorination by GR, but also provide a feasible approach for practical remediations of TCE-contaminated groundwater using GR-NG mixture.

Oxide of porous graphitized carbon as recoverable functional adsorbent that removes toxic metals from water.

The numerous oxygenated functional groups on graphite oxide (GO) make it a promising adsorbent for toxic heavy metals in water. However, the GO prepared from natural graphite is water-soluble after exfoliation, making its recovery for reuse extremely difficult. In this study, porous graphitized carbon (PGC) was oxidized to fabricate a GO-like material, PGCO. The PGCO showed an O/C molar ratio of 0.63, and 8.4% of the surface carbon species were carboxyl, exhibiting enhanced oxidation degree compared to GO. The small PGCO sheets were intensely aggregated chemically, yielding an insoluble solid easily separable from water by sedimentation or filtration. Batch adsorption experiments demonstrated that the PGCO afforded significantly higher removal efficiencies for heavy metals than GO, owing to the former's greater functionalization with oxygenated groups. An isotherm study suggested that the adsorption obeyed the Langmuir model, and the derived maximum adsorption capacities for Cr3+, Pb2+, Cu2+, Cd2+, Zn2+, and Ni2+ were 119.6, 377.1, 99.1, 65.2, 53.0, and 58.1 mg/g, respectively. Furthermore, the spent PGCO was successively regenerated by acid treatment. The results of the study indicate that PGCO could be an alternative adsorbent for remediating toxic metal-contaminated waters.

Calcium Sulfite Solids Activated by Iron for Enhancing As(III) Oxidation in Water.

Desulfurized gypsum (DG) as a soil modifier imparts it with bulk solid sulfite. The Fe(III)-sulfite process in the liquid phase has shown great potential for the rapid removal of As(III), but the performance and mechanism of this process using DG as a sulfite source in aqueous solution remains unclear. In this work, employing solid CaSO3 as a source of SO32-, we have studied the effects of different conditions (e.g., pH, Fe dosage, sulfite dosage) on As(III) oxidation in the Fe(III)-CaSO3 system. The results show that 72.1% of As(III) was removed from solution by centrifugal treatment for 60 min at near-neutral pH. Quenching experiments have indicated that oxidation efficiencies of As(III) are due at 67.5% to HO•, 17.5% to SO5•- and 15% to SO4•-. This finding may have promising implications in developing a new cost-effective technology for the treatment of arsenic-containing water using DG.