Graphitic carbon nitride (g-CN) is an emerging metal-free photocatalyst for solar energy conversion via water splitting and CO2 fixation. Herein, we used preheated melamine as a starting material in combination with the salt melt method to synthesize a crystalline tri-s-triazine-based g-CN. The as-obtained sample exhibited high stability and photocatalytic activity toward hydrogen and oxygen production from water splitting. In addition, by adding phosphate to mimic natural photosynthetic environment, the apparent quantum yield (AQY) for the hydrogen production reached 50.7% at 405 nm, which is the highest value ever reported for conjugated carbon nitride polymers in hydrogen evolution photocatalysis. The results of this study demonstrate that crystalline covalent tri-s-triazine frameworks hold great promise for solar energy applications.

Two-dimensional-layered heterojunctions have attracted extensive interest recently due to their exciting behaviours in electronic/optoelectronic devices as well as solar energy conversion systems. However, layered heterojunction materials, especially those made by stacking different monolayers together by strong chemical bonds rather than by weak van der Waal interactions, are still challenging to fabricate. Here the monolayer Bi2WO6 with a sandwich substructure of [BiO]+–[WO4]2−–[BiO]+ is reported. This material may be characterized as a layered heterojunction with different monolayer oxides held together by chemical bonds. Coordinatively unsaturated Bi atoms are present as active sites on the surface. On irradiation, holes are generated directly on the active surface layer and electrons in the middle layer, which leads to the outstanding performances of the monolayer material in solar energy conversion. Our work provides a general bottom-up route for designing and preparing novel monolayer materials with ultrafast charge separation and active surface.

Polymeric carbon nitride (PCN), in either triazine or heptazine form, has been regarded as a promising metal-free, environmentally benign, and sustainable photocatalyst for solar hydrogen production. However, PCN in most cases only exhibits moderate activity owing to its inherent properties, such as rapid charge carrier recombination. Herein we present a triazine-heptazine copolymer synthesized by simple post-calcination of PCN in eutectic salts, that is, NaCl/KCl, to modulate the polymerization process and optimize the structure. The construction of an internal triazine-heptazine donor-acceptor (D-A) heterostructure was affirmed to significantly accelerate interface charge transfer (CT) and thus boost the photocatalytic activity (AQY=60 % at 420 nm). This study highlights the construction of intermolecular D-A copolymers in NaCl/KCl molten salts with higher melting points but in the absence of lithium to modulate the chemical structure and properties of PCN.

Ti-substituted NH2-Uio-66(Zr/Ti) prepared by using a post-synthetic exchange (PSE) method showed enhanced photocatalytic performance for both CO2 reduction and hydrogen evolution under visible light. Density functional theory (DFT) calculations and electron spin resonance (ESR) results reveal that the introduced Ti substituent acts as a mediator to facilitate electron transfer, which results in enhanced performance.

In semiconductor-mediated photocatalysis, the optical property of semiconductors is a key parameter and closely related to the conversion efficiency of solar energy. However, endeavors in achieving a wide spectral response of semiconductors are still limited in impurity incorporation or using other assistants. Here, we report on a structuredistortion-induced extension in the optical absorption of conjugated polymer semiconductors without relying on any extra species, by taking a typical example of twodimensional graphitic carbon nitride (g-C 3 N 4 ) nanosheets. Experimental and theoretical calculation results both identified the close relationship between the band structure and the structural distortion and the amount of the layers, while keeping in-plane fundamental units intact and the connecting mode invariable during the peeling process. Photocatalytic activity was evaluated toward hydrogen evolution over different samples with visible light. The results showed that distorted g-C 3 N 4 exhibited higher activity and its wavelength-dependence activity can be extended to 550 nm with desirable H 2 production. This finding offers a new channel for researchers to design a polymer with photocatalytic activity under its extending visible spectrum.

Exciton binding energy has been regarded as ac rucial parameter for mediating charge separation in polymeric photocatalysts.M inimizing the exciton binding energy of the polymers can increase the yield of charge-carrier generation and thus improve the photocatalytic activities,b ut the realization of this approach remains ag reat challenge. Herein, aseries of linear donor-acceptor conjugated polymers has been developed to minimizethe exciton binding energy by modulating the charge-transfer pathway. The results reveal that the reduced energy loss of the charge-transfer state can facilitate the electron transfer from donor to acceptor,a nd thus,m ore electrons are ready for subsequent reduction reactions.The optimizedpolymer,FSO-FS,exhibits aremarkable photochemical performance under visible light irradiation.Hydrogen evolution using nanoparticulate semiconductors has great potential for future green and sustainable fuel production from water and sunlight. [1, 2] Conjugated polymers (CPs), including carbon nitride, [3] COFs, [4] CTFs, [5] CMPs, [6] and linear polymers, [7] have recently emerged as anew family of semiconductor photocatalysts,o wing to their advantages, such as tunable structure and properties,e ase of fabrication, environmental friendliness,a nd absence of noble metals.T o date,c onsiderable advances have been achieved by rational design of the structure and by tailoring of the properties of the CPs. [8] Nevertheless,because of their undesirably high exciton binding energy (E b ,t ypically > 100 meV), [9] most of the polymeric photocatalysts show only moderate photocatalytic activities,p articularly in comparison with their inorganic counterparts.Recently,i nspired by the rapid charge transfer in donoracceptor (D-A) heterojunction based solar cells,such aD-A construction has also been applied to boost the charge mobility of conjugated polymeric photocatalysts by controlling the local structure of the polymers. [10] It is well established that in aD -A based CP,t he charges tend to spontaneously migrate to the acceptor because of the larger energy of the light-excited excitons (E exc )c ompared to those of the charge transfer (CT) state (E CT )a nd E LUMO of the acceptor (see Scheme 1a). [11] Clearly,the overall amount of charge arriving Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

The combination of lone-pair effects on Pb(2+) cations and the smaller electronegativity of I(-) anions into the pentaborate framework generates a phase-matchable material, Pb(2)B(5)O(9)I, with the largest powder SHG response among borates, about 13.5 times that of KDP (KH(2)PO(4)), and transparency over the near-UV to middle-IR region. DFT calculations on electronic structure and cutoff-energy-dependent SHG coefficients confirm these origins.

of semiconductor photocatalysts to retard the recombination of charge carriers and enhance surface reaction rates. [13][14][15] Among various kinds of cocatalysts, Pt often shows the best performance. However, practical application of Pt-based cocatalysts is limited by their scarcity and high cost. [16] Therefore, development of highly active and cost-efficient alternatives to Pt is urgently needed. A large number of transition metals (e.g., iron, cobalt, nickel, molybdenum, and tungsten) and their derivative compounds have been studied. Fu and colleagues have integrated CdS with MoS 2 and obtained much improved hydrogen evolution activity. [17] However, the performances of which are still far from satisfactory because of the low active surface areas and sluggish separation of electron-hole pairs. [18][19][20] Thus, designing novel materials which can address these problems may lead to the discovery of non-noble metal cocatalysts with enhanced performance. Metal oxide clusters, constructed by a small number of atoms, can largely expose active metal sites. [21] Moreover, when loaded onto semiconductor photocatalysts, metal oxide clusters can induce discrete energy bands to trap charge carriers and promote the separation of electrons and holes. Regarding such unique properties, cluster cocatalysts show the potential to boost the activity of semiconductor photocatalysts for solar water splitting.The performance of cluster cocatalysts is significantly influenced by the number and coordination environment of the active atoms. [22][23][24] Therefore, it is essential to establish a synthetic method to precisely control the configuration of clusters decorated on the surface of semiconductor photocatalysts at atomic level. [25,26] Herein, a bottom-up strategy is developed to decorate ultrasmall molybdenum-oxygen (MoO x ) clusters onto the surface of CdS nanowires (NWs). The decorated clusters with finely controlled size and configuration greatly enhance the photocatalytic H 2 evolution efficiency of CdS NWs.CdS NWs are first synthesized through a solvothermal approach. [27] X-ray diffraction (XRD) pattern of as-prepared sample shows characteristic peaks of CdS with hexagonal wurtzite crystal structure ( Figure S1, Supporting Information). Field-emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and high-resolution TEM (HRTEM) images indicate the successful synthesis of CdS NWs with good crystallinity (Figure S2, Supporting Information). The average diameter of the CdS NWs is about 75 nm (Figure S3, Supporting Information). MoO x clusters are then decorated To enhance the performance of semiconductor photocatalysts, cocatalysts are used to accelerate surface reactions. Herein, ultrasmall molybdenumoxygen (MoO x ) clusters are developed as a novel non-noble cocatalyst, which significantly promotes the photocatalytic hydrogen generation rate of CdS nanowires (NWs). As indicated by extended X-ray absorption fine structure analysis, direct bonds are formed between CdS NWs and MoO x clusters,...