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Covalent heptazine frameworks (CHFs) are widely utilized in the recent years as potential photocatalysts. However, their limited conjugated structures, low crystallinity and small surface areas have restricted the practical photocatalysis performance. Along this line, we report herein the synthesis of a kind of mixed crystalline CHF (m‐CHF‐1) with built‐in heterojunction structure, which can efficiently catalyze the formic acid dehydrogenation by visible light driven photocatalysis. The m‐CHF‐1 is synthesized from 2,5,8‐triamino‐heptazine and dicyanobenzene (DCB) in the molten salts, in which DCB plays as organic molten co‐solvent to promote the rapid and ordered polymerization of 2,5,8‐triamino‐heptazine. The m‐CHF‐1 is formed by embedding phenyl‐linked heptazine (CHF−Ph) units in the poly(heptazine imide) (PHI) network similar to doping. The CHF−Ph combined with PHI form an effective type II heterojunction structure, which promote the directional transfer of charge carriers. And the integration of CHF−Ph makes m‐CHF‐1 have smaller exciton binding energy than pure PHI, the charge carriers are more easily dissociated to form free electrons, resulting in higher utilization efficiency of the carriers. The largest hydrogen evolution rate reaches a value of 42.86 mmol h−1 g−1 with a high apparent quantum yield of 24.6 % at 420 nm, which surpasses the majority of other organic photocatalysts. [ABSTRACT FROM AUTHOR]

We report herein the electron transfer process of a novel supramolecular dyads composed of zinc tetraphenylporphyrin (ZnTPP) and zinc 5,15‐dinonyl‐10,20‐diphenylporphyrin (ZnDPP), as electron donors, and ethyl(4‐pyridyl) coumarin‐3‐carboxylate (EPCC), as an electron acceptor, through metal‐ligand coordination bond in dichloromethane. The optical absorption studies revealed the formation of the moderate stable supramolecular donor‐acceptor dyads. The fluorescence measurements showed a significant fluorescence quenching of the singlet‐excited state of the singlet‐excited states of ZnTPP and ZnDPP upon addition of different amounts of EPCC. Such quenching behavior could be attributed to the electron transfer from the singlet‐excited state of porphyrin to EPCC. The bimolecular quenching rates were determined to be 1.98×1012 and 7.59×1012 L mol−1 s−1 for ZnTPP‐EPCC and ZnDPP‐EPCC, respectively, respectively. The fluorescence lifetime measurements suggest fast and efficient intra‐supramolecular electron transfer from the singlet states of porphyrin derivatives to EPCC. Furthermore, the formation of the supramolecular dyads was confirmed by the Raman technique and computational studies. The finding that the examined zinc porphyrin ‐ coumarin supramolecular dyads absorb light in a wide range of UV‐visible spectrum, fast and efficient electron transfer render the examined supramolecular dyad as simple models for the reaction centers of the artificial photosynthetic systems. [ABSTRACT FROM AUTHOR]

Herein, a highly sensitive nanosensor was developed by covalent grafting of Schiff base. (E)‐2,3‐dimethyl‐1‐phenyl‐4‐(pyridin‐2‐ylmethyleneamino)‐1,2‐dihydropyrazol‐5‐one (DPPDO) on the surface of mesoporous titanium, Mes‐TiO2, via an aminopropyl bridge to get Mes‐TiO2‐NH2/DPPDO. The effective grafting was validated by different spectroscopic techniques. Using absorption, and emission measurements, the colorimetric and optical detection behaviors of several metal ions such as Mn2+, Fe3+, Zn2+, Ag+, Cd2+, Hg2+, Al3+, and Pb2+ were investigated. By dispersing the nanosensor in an aqueous solution containing the metal ions of interest, the resulting solid materials exhibited high binding to Fe3+ ions compared to other metal ions, resulting in dramatic fluorescence intensity up to 87 %. It showed quenching and yellow discoloration. When 0.2 M hydrochloric acid was added to the produced nanosensor‐Fe complex, the effect of the investigated nanosensor was reversible, restoring the original absorption and emission spectra of the free sensor. It is shown that there are solvent effects are also discussed for solvents of different polarities. Fluorescence quantum yields, fluorescence lifetimes, binding constants, and limit of detection were determined. In addition, reusability was evaluated to determine the adsorption efficacy of the nanosensor and was found to be effective seven times, suggesting that nanosensor is potential one for metal ion detection. [ABSTRACT FROM AUTHOR]

Because of its sustainability and cleanliness, hydrogen has recently been a research focus as a potential fuel. One promising way to produce hydrogen is water electrolysis in an alkaline solution. However, this process requires much energy to split the H–OH bond and transfer multiple electrons/protons. To overcome this challenge, catalytic electrodes have been developed to reduce the energy needed and maintain sustainable water electrolysis. This study explores the potential of utilizing a two-dimensional nickel-based cyanide coordination polymer (2D Ni-CP) precursor to synthesize effective Ni-based inorganic nanostructured electrodes. Various types of electrodes, including Ni-O, Ni-S, Ni-Se, and Ni-P, are synthesized through direct thermal treatment of the coordination polymer. The performance of the as-prepared materials in the hydrogen evolution process (HER) in an alkaline medium is examined. Ni-P demonstrates the most promising HER performance with an overpotential of 266 mV at 10 mA cm−2 and a Tafel slope of 186 mV dec−1. These results are compared to those of the benchmark expensive and scarce Pt/C-40% catalyst (38 mV and 48 mV dec−1) examined under identical conditions. Additionally, Ni-P shows outstanding HER durability over four days, as reflected by chronopotentiometry measurements. [ABSTRACT FROM AUTHOR]