RESUMO
Covalent organic frameworks (COFs), which have layered stacking structures, extended π-conjugation, and periodic frameworks have become a promising class of materials for a wide range of applications. However, their synthetic pathways frequently need high temperatures, enclosed systems under high pressures, an inert atmosphere, and extended reaction time, which restrict their practicality in real-world applications. Herein, the use of gamma irradiation is presented to synthesize highly crystalline COFs at room temperature under an open-air condition within a short time. This is demonstrated that there is no significant difference in crystallinity of COFs by gamma irradiation under air, N2 or Ar atmosphere conditions. Moreover, this approach can successfully fabricate COFs in the vessel with different degrees of transparency or even in a plastic container. Importantly, this strategy is applicable not only to imine linkage of COFs but also effective to the imide linkages of COFs. Most importantly, these COFs demonstrate improved crystallinity, surface area, and thermal stability in comparison to the corresponding materials synthesized via the solvothermal method. Finally, a COF synthesized through gamma irradiation exhibits remarkable photocatalytic activity in promoting the sacrificial hydrogen evolution from water, displaying a more catalytic efficiency compared with that of its solvothermal analogue.
RESUMO
Converting solar energy into hydrogen energy using conjugated polymers (CP) is a promising solution to the energy crisis. Improving water solubility plays one of the critical factors in enhancing the hydrogen evolution rate (HER) of CP photocatalysts. In this study, a novel concept of incorporating hydrophilic side chains to connect the backbones of CPs to improve their HER is proposed. This concept is realized through the polymerization of carbazole units bridged with octane, ethylene glycol, and penta-(ethylene glycol) to form three new side-chain-braided (SCB) CPs: PCz2S-OCt, PCz2S-EG, and PCz2S-PEG. Verified through transient absorption spectra, the enhanced capability of PCz2S-PEG for ultrafast electron transfer and reduced recombination effects has been demonstrated. Small- and wide-angle X-ray scattering (SAXS/WAXS) analyses reveal that these three SCB-CPs form cross-linking networks with different mass fractal dimensions (f) in aqueous solution. With the lowest f value of 2.64 and improved water/polymer interfaces, PCz2S-PEG demonstrates the best HER, reaching up to 126.9 µmol h-1 in pure water-based photocatalytic solution. Moreover, PCz2S-PEG exhibits comparable performance in seawater-based photocatalytic solution under natural sunlight. In situ SAXS analysis further reveals nucleation-dominated generation of hydrogen nanoclusters with a size of ≈1.5 nm in the HER of PCz2S-PEG under light illumination.
RESUMO
A hybrid composite of organic-inorganic semiconductor nanomaterials with atomic Au clusters at the interface decoration (denoted as PF3T@Au-TiO2 ) is developed for visible-light-driven H2 production via direct water splitting. With a strong electron coupling between the terthiophene groups, Au atoms and the oxygen atoms at the heterogeneous interface, significant electron injection from the PF3T to TiO2 occurs leading to a quantum leap in the H2 production yield (18 578 µmol g-1 h-1 ) by ≈39% as compared to that of the composite without Au decoration (PF3T@TiO2 , 11 321 µmol g-1 h-1 ). Compared to the pure PF3T, such a result is 43-fold improved and is the best performance among all the existing hybrid materials in similar configurations. With robust process control via industrially applicable methods, it is anticipated that the findings and proposed methodologies can accelerate the development of high-performance eco-friendly photocatalytic hydrogen production technologies.
RESUMO
Conjugated polymers (CPs) have recently gained increasing attention as photocatalysts for sunlight-driven hydrogen evolution. However, they suffer from insufficient electron output sites and poor solubility in organic solvents, severely limiting their photocatalytic performance and applicability. Herein, solution-processable all-acceptor (A1 -A2 )-type CPs based on sulfide-oxidized ladder-type heteroarene are synthesized. A1 -A2 -type CPs showed upsurging efficiency improvements by two to three orders of magnitude, compared to their donor-acceptor -type CP counterparts. Furthermore, by seawater splitting, PBDTTTSOS exhibited an apparent quantum yield of 18.9% to 14.8% at 500 to 550 nm. More importantly, PBDTTTSOS achieved an excellent hydrogen evolution rate of 35.7 mmol h-1 g-1 and 150.7 mmol h-1 m-2 in the thin-film state, which is among the highest efficiencies in thin film polymer photocatalysts to date. This work provides a novel strategy for designing polymer photocatalysts with high efficiency and broad applicability.
RESUMO
Photocatalytic water splitting is attracting considerable interest because it enables the conversion of solar energy into hydrogen for use as a zero-emission fuel or chemical feedstock. Herein, we present a universal approach for inserting hydrophilic non-conjugated segments into the main-chain of conjugated polymers to produce a series of discontinuously conjugated polymer photocatalysts. Water can effectively be brought into the interior through these hydrophilic non-conjugated segments, resulting in effective water/polymer interfaces inside the bulk discontinuously conjugated polymers in both thin-film and solution. Discontinuously conjugated polymer with 10 mol% hexaethylene glycol-based hydrophilic segments achieves an apparent quantum yield of 17.82% under 460 nm monochromatic light irradiation in solution and a hydrogen evolution rate of 16.8 mmol m-2 h-1 in thin-film. Molecular dynamics simulations show a trend similar to that in experiments, corroborating that main-chain engineering increases the possibility of a water/polymer interaction. By introducing non-conjugated hydrophilic segments, the effective conjugation length is not altered, allowing discontinuously conjugated polymers to remain efficient photocatalysis.
RESUMO
Organic semiconducting polymers exhibited promising photocatalytic behavior for hydrogen (H2) evolution, especially when prepared in the form of polymer dots (Pdots). However, the Pdot structures were formed using common nonconjugated amphiphilic polymers, which have a negative effect on charge transfer between photocatalysts and reactants and are unable to participate in the photocatalytic reaction. This study presents a new strategy for constructing binary Pdot photocatalysts by replacing the nonconjugated amphiphilic polymer typically employed in the preparation of polymer nanoparticles (Pdots) with a low-molecular-weight conjugated polyelectrolyte. The as-prepared polyelectrolyte/hydrophobic polymer-based binary Pdots truly enhance the electron transfer between the Pt cocatalyst and the polymer photocatalyst with good water dispersibility. Moreover, unlike the nonconjugated amphiphilic polymer, the photophysics and mechanism of this photocatalytic system through time-correlated single-photon counting (TCSPC) and transient absorption (TA) measurements confirmed the Förster resonance energy transfer (FRET) between the polyelectrolyte as a donor and the hydrophobic polymer as an acceptor. As a result, the designated binary Pdot photocatalysts significantly enhanced the hydrogen evolution rate (HER) of 43â¯900 µmol g-1 h-1 (63.5 µmol h-1, at 420 nm) for PTTPA/PFTBTA Pdots under visible-light irradiation.
RESUMO
Tuberculosis is a common infectious mycobacterial disease having a wide range of clinical and serological manifestations that are similar to rheumatic disease. Differential diagnosis is a crucial aspect in any rheumatic disease as many other infectious diseases portray clinical similarities and autoantibody positivity. Our case report illustrates of a young woman just after the delivery of a child presented an unusual case of extrapulmonary tuberculosis infection initially misdiagnosed as systemic lupus erythematosus (SLE).
