Photocatalytic hydrogen peroxide (H 2 O 2 ) generation using H 2 O and O 2 , when coupled with simultaneous environmental remediation, offers an attractive strategy to enhance solar‐to‐chemical conversion efficiency by improving charge‐carrier utilization and minimizing energy losses. Among the various photocatalysts (PCs) explored, graphitic carbon nitrides (g‐C 3 N 4 ) have garnered significant attention owing to their metal‐free composition, chemical stability, and environmental compatibility. However, their practical performance remains constrained by intrinsic limitations, such as rapid electron–hole recombination, sluggish surface reaction kinetics, and low selectivity toward the oxygen reduction reaction. Addressing these challenges requires a detailed understanding of the underlying reaction mechanisms and the structure–activity relationships governing the photocatalytic behavior. This minireview provides a concise overview of the fundamental pathways involved in photocatalytic H 2 O 2 production and highlights recent advancements in metal‐free modification strategies for g‐C 3 N 4 . Particular emphasis is placed on how these modifications impact key photocatalytic properties, such as light absorption, charge separation and transport, and surface reactivity. Importantly, the review discusses the emerging integration of in situ H 2 O 2 generation with environmental remediation processes, including pollutant degradation, biomass oxidation, and microbial disinfection. By linking catalyst design principles with practical remediation outcomes, this work aims to offer guidance for the rational development of efficient carbon nitride–based PCs for sustainable, decentralized environmental applications.

Increasing the emission quantum efficiency of organic compounds composed of ubiquitous elements will lead to the production of bright organic light‐emitting diodes. One solution to this issue is to utilize the triplet exciton, and excited‐state intramolecular proton transfer has recently attracted attention. In this study, we investigated the photophysical properties of compound 1 , which has three alternating benzimidazole and hydroxy groups substituted on the benzene ring and can form hexapole hydrogen bonds. 1 showed an emission maximum at 440 nm, and solvent polarity had a small influence. The emission intensity increased under an argon atmosphere, and the degassed sample solution showed a long‐lived component with a time constant of 15 μs. The emission spectrum at 80 K, which had a maximum at 440 nm and a shoulder around 460 nm, implies the simultaneous fluorescence and phosphorescence emissions. Variable temperature lifetime measurements suggested that phosphorescence disappears at 160 K, and thermally activated delayed fluorescence is observed at elevated temperatures. Theoretical calculations revealed that all‐keto form 1A is photoexcited, generating 1B * after one proton transfer, and thermally activated delayed fluorescence is observed via reverse intersystem crossing from higher‐lying triplet states (T 2 and T 3 ) to the singlet state (S 1 ).

Photoelectrochemical water splitting is a promising route to sustainable hydrogen production, but it requires semiconductor electrodes with optimal bandgap, proper band‐edge alignment to the water redox potentials, and high corrosion resistance. Cubic silicon carbide (3C‐SiC) is a compelling candidate due to its near‐ideal bandgap energy and excellent chemical stability. Here, we systematically characterize SiC photoelectrodes comprising of n‐type and p‐type 3C‐SiC thin films grown on Si substrates of matching dopant type. Linear‐sweep voltammetry and electrochemical impedance spectroscopy yield the key photoelectrochemical parameters including the flat‐band potential and open‐circuit potential. Ultraviolet photoelectron spectroscopy and low‐energy inverse photoelectron spectroscopy provide the valence‐band maximum, conduction‐band minimum, Fermi level positions, and bandgap energies. Together, these results elucidate the detailed energy band landscapes for both n‐ and p‐3C‐SiC/electrolyte interfaces. The energy diagrams explain the observed behavior with and without illumination, confirming that n‐doped 3C‐SiC functions as efficient photoanode for oxygen evolution while p‐doped 3C‐SiC acts as photocathode for hydrogen evolution in neutral aqueous electrolyte. Establishing these quantitative band‐edge alignments provides a blueprint for designing durable, bias‐free tandem PEC architectures. Given the scalability and stability of SiC, these insights advance pathways toward cost‐effective, large‐scale green‐hydrogen production with a reduced environmental footprint.

Methanol shows great potential as a liquid hydrogen carrier, and its steam reforming offers a promising route for on‐site hydrogen (H 2 ) production. However, this process typically requires high temperatures. In this study, we developed a thermo‐photocatalytic (TPC) system based on Au‐modified TiO 2 photocatalysts designed to enable methanol steam reforming (MSR) at low temperatures without sacrificing efficiency. The photocatalysts were evaluated for MSR activity under ultraviolet (UV) irradiation (365 nm) across a range of temperatures. Compared with TiO 2 brookite and TiO 2 P25, the low‐crystalline 1.0 wt% Au/TiO 2 anatase catalyst exhibited exceptional TPC performance for MSR despite its low crystallinity. It achieved a hydrogen production rate of 370 mmol g −1 h −1 W −1 at 150°C, with a high apparent quantum efficiency (AQE) of 26.9%. Moreover, complete MSR was achieved with CO‐free hydrogen production. The superior TPC performance of the low‐crystalline TiO 2 is primarily attributed to its higher surface area, stronger electronic interaction with Au, and lower apparent activation energy. Unlike conventional photocatalysis, a linear relationship between light intensity and hydrogen production rate was observed for the TPC process, indicating that energetic electrons were responsible for the TPC reaction. The interplay between thermal and photochemical processes enhances the overall TPC efficiency, thereby improving the MSR performance.

The growing demand for efficient and sustainable water purification technologies has intensified because of the increasing outflow of toxic and nonbiodegradable organic pollutants from industrial activities. Conventional treatment methods often require high energy input or chemical additives, leading to high costs and environmental concerns. Photoelectrochemical (PEC) systems, which utilize solar energy to drive pollutant degradation, offer promising alternatives. In this study, we demonstrate the fabrication of Sb‐incorporated Cu 2 O photocathodes via a simple electrochemical deposition method to enhance PEC water purification performance. Cu 2 O is a favorable p‐type semiconductor with strong visible‐light absorption and an earth‐abundant composition. However, its application is limited by poor crystallinity and randomly distributed grain boundaries that restrict charge transport. Incorporation of antimony promoted preferential (111) crystal orientation of Cu 2 O, increased nucleation density, and the formation of vertical grain boundaries perpendicular to the substrate. The photocathode with 0.75 mol% Sb incorporation exhibited outstanding PEC activity, reaching a photocurrent density of ∼2.8 mA cm −2 at −0.35 V Ag/AgCl under 1‐sun illumination. This enabled the complete degradation of methyl orange within 90 min without any overlayers or posttreatment, while maintaining excellent stability. This study offers a scalable, low‐cost strategy for constructing high‐performance Cu 2 O‐based photocathodes for solar‐driven environmental remediation.

The complexation behaviors between four local anesthetics and pagoda[5]arene were investigated using 1 H NMR spectroscopy, fluorescence spectroscopy, and density functional theory calculations. Among the four selected local anesthetics, only tetracaine and procaine were found to form stable 1:1 host–guest complexes with pagoda[5]arene. Structural analyses revealed that the alkylammonium moieties of these two ester‐type anesthetic guest molecules could be encapsulated within the electron‐rich cavity of pagoda[5]arene. The stability of the resulting complexes arises from the synergistic contributions of multiple noncovalent interactions, including C–H··· π interactions, π ··· π interactions, and hydrogen bonding. This selective binding behavior provides new practical opportunities for applications in pharmaceutical analysis, clinical safety monitoring, and drug quality control.

Solar‐driven generation of reactive oxygen species via photocatalytic membranes is a promising technology for the photodegradation of water‐borne pollutants. Here, titanium dioxide (TiO 2 ) ultrathin films (11.9–28.05 nm) were grown on polytetrafluoroethylene (PTFE) and quartz‐fiber filter (QFF) membranes via atomic layer deposition. The as‐deposited (250°C) films were i) furnace annealed (300°C–1100°C) for 1 h or ii) via rapid thermal annealing (300–500°C) for 3 min. The presence of Ti coating onto/into QFF was confirmed, four times more than on PTFE. As‐deposited TiO 2 films on QFF exhibited the crystalline phase of anatase, while no peaks were observed on PTFE. Films annealed on QFF at higher temperatures did not exhibit a mixed anatase‐rutile phase, regardless of thickness. The films on QFF also exhibited significantly higher absorption of ultraviolet light (<400 nm) compared to the films on PTFE, which had limited absorption (<360 nm). Nonstoichiometric TiO 2− x films exhibited broad absorption from ultraviolet to the near infrared. The annealed films on QFF demonstrated high photocatalytic performance of about 88%–94% removal of methyl orange and 90%–97% for tartrazine 85 (compared to films on PTFE with 36% and 18%, respectively). The TiO 2− x films demonstrated improved performance compared to pure anatase TiO 2 , paving the way for improved photocatalytic membrane performance.

The photophysical properties of two positional isomers of dinaphthyl‐9‐phenylcarbazoles (2,7‐DNpPCz and 3,6‐DNpPCz) were systematically investigated in solution and solid states. Experimental measurements revealed a pronounced positional dependence, although both compounds exhibit fluorescence in solution and the solid state. On average, the 2,7‐isomers exhibit larger fluorescence rate values than the 3,6‐isomers, although the magnitude of this difference varies among individual compounds. To gain mechanistic insight, density function theory (DFT) and time‐dependence DFT calculations were performed at the (TD)‐B3LYP/6‐31+G(d) level. The results show that 2,7‐DNpPCz derivatives possess delocalized frontier orbitals and large oscillator strengths for the S 1 ← S 0 transition, whereas 3,6‐DNpPCz derivatives exhibit smaller oscillator strengths with mixed orbital contributions, leading to weaker transition probabilities. These combined findings demonstrate that substitution geometry critically governs radiative decay dynamics in carbazole‐based luminophores and provide valuable guidelines for the molecular design of efficient solid‐state organic emitters.