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[Display omitted] A series of dehydrated MoS 2 /UiO-66(SH) 2 (MS/UiS) composites has been prepared as photocatalysts for N 2 fixation. Typically, 10% MS/UiS exhibits the best performance with an NH 4 + yield rate of 54.08 μmol∙g−1∙h−1. 15N isotope test confirmed that the sample 10% MS/UiS was most effective for reducing N 2 to ammonia. Such enhanced activity was due to the presence of abundant unsaturated Zr and Mo sites which would synergistically promote the adsorption and activation of N 2. The photogenerated electrons would transfer to the unsaturated Zr-O clusters while part of photogenerated electrons at the interface migrate to MS via MoVI-O interactions between MS and UiS. These two electron transfer pathways effectively promote the separation of photogenerated carriers. The activated N 2 is reduced to ammonia by the synergistic effect of protonated hydrogen and photogenerated electrons. Finally, a possible N 2 fixation mechanism is proposed which emphasizes the significant roles of nitrogen activation and interface interaction in composites photocatalyst for improving photocatalytic performance. [ABSTRACT FROM AUTHOR]

Efficient visible-light-driven selective oxidation of benzyl alcohol to benzaldehyde over Pt/5MnNS. [Display omitted] • Multicomponent Pt/Mn-Bi 4 Ti 3 O 12 ultrathin nanosheets were successfully constructed. • Pt/5MnNS exhibited high benzaldehyde yield rate (1180 μmol·g−1·h−1). • Surface Ti4+δ sites as stronger Lewis acid sites effectively activated benzyl alcohol. • The structure–function relationship for the multicomponent Pt/5MnNS was revealed. Herein, a series of Pt nanoparticles modificatory Mn doped Bi 4 Ti 3 O 12 ultrathin nanosheets (Pt/MnNS) are constructed as a surface functionalized photocatalyst for the visible-light-driven selective benzyl alcohol (BA) oxidation. Especially, Pt/5MnNS shows the best performance with a benzaldehyde (BD) yield rate of 1180 μmol·g−1·h−1 and a selectivity of 99.9 %. More importantly, experimental results reveal that Mn doping not only extends the optical absorption range of the photocatalyst to the visible region, but also induces the formation of more surface Ti4+δ atoms. Those Ti4+δ atoms as stronger Lewis acid centers achieve more conspicuous adsorption and activation of BA via the C O⋯Ti coordination. It makes the deprotonation of BA by photogenerated holes be easier. Meanwhile, Pt nanoparticles significantly promote the separation and transfer of the photogenerated carriers for supporting the formation of superoxide and carbon-centered radicals. Thus, the photocatalytic BA oxidation efficiency is markedly improved by surface multicomponent synergistic effect. [ABSTRACT FROM AUTHOR]

[Display omitted] Ultrathin Bi 4 Ti 3 O 12 nanosheets (NS) with the thickness about 3.9 nm were successfully synthesized by a hydrothermal method and were used as a photocatalyst for the oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). The photocatalytic performance of NS is about 8 times higher than that of bulk Bi 4 Ti 3 O 12. In-situ FTIR of pyridine adsorption and NH 3 -TPD reveal that NS has more surface Lewis acid sites (Ti4+) for the adsorption and activation of BA. The photogenerated electrons (e-) and holes (h+) of NS can be fully used to produce the superoxide radicals and carbon-centered radicals, respectively. The monolayer nanosheet structure of NS not only greatly promotes the separation of photogenerated carriers, but also achieves the efficient activation of BA molecules via the C O⋯Ti coordination. This work successfully reveals the surface/interface interactions between the surface active sites of a photocatalyst and the reactive molecules via using ultrathin nanosheet as a molecular platform. [ABSTRACT FROM AUTHOR]

The multifunctional photocatalysts (Au-Pd/SnNb 2 O 6 ultrathin nanosheets) are developed for selective hydrogenation of cinnamaldehyde to hydrocinnamaldehyde under visible light. The superior catalytic performance is attributed to a synergistic effect of Au, Pd nanoparticles, and SnNb 2 O 6 ultrathin nanosheets. [Display omitted] • Au-Pd/SnNb 2 O 6 (SN) as photocatalysts for selective hydrogenation of cinnamaldehyde. • The C = C of cinnamaldehyde would be absorbed on the surface Lewis acid sites of SN. • Photogenerated electrons promoted H 2 dissociation on Pd, Au reduced overhydrogenation. • The superior performance is attributed to a synergistic effect of catalyst component. Au-Pd bimetallic nanoparticles (NPs) supported on SnNb 2 O 6 ultrathin nanosheets (SN) were developed as multifunctional photocatalysts for the selective hydrogenation of cinnamaldehyde (CAL) to hydrocinnamaldehyde (HCAL) under visible light irradiation. A representative catalyst (Au 6 -Pd 1 /SN) exhibits optimum performances with 99.8% conversion and 91.0% selectivity. The structure and surface properties of the prepared samples were revealed by SEM, TEM, BET, TPD, XPS, and EPR. The results of in situ FTIR spectra and NH 3 -TPD reveal that the rich surface Lewis acid sites on SN can chemisorb and activate CAL via the C = C...Nb coordination. EPR experiments indicate that H 2 would dissociate to activated H atoms on Pd NPs following a photopromoted surface catalytic process. Experimental results suggest that Au NPs reduce the over hydrogenation of HCAL by inhibiting the formation of Pd-H species. The superior catalytic performance is attributed to a synergistic effect of Au, Pd NPs and SN. Finally, a possible synergetic mechanism for Au-Pd/SN is proposed to illustrate the photocatalytic process. This work offers a reference to guide a novel and more effective photocatalyst design for precise organic synthesis driven by sunlight. [ABSTRACT FROM AUTHOR]

Au nanoparticles-anchored defective DUT-67(Zr) MOF was fabricated for photocatalytic transformation of amines to imines and the synergetic mechanism combining the plasmon with the molecular activation was illustrated. [Display omitted] Designing efficient metal organic frameworks (MOF)-based photocatalysts has recently attracted wide attention. In this work, Au nanoparticles(NPs)-decorated defective DUT-67(Zr) (Au@DUT-67(Zr)) with enlarged channels was successfully fabricated and achieved 7.5 times higher conversion than Au NPs-decorated UiO-66(Zr) (Au@UiO-66(Zr)) for photocatalytic selective oxidation of amines to imines driven by visible light. Au NPs are more effectively fixed on DUT-67(Zr) due to its partially hollow structure. Au@DUT-67(Zr) possesses more active sites including unsaturated Zr atoms and oxygen vacancies (VO) than Au@UiO-66(Zr). In situ Fourier transform infrared (FTIR) spectrum reveals that benzylamine is activated on unsaturated Zr sites via H N ... Zr species, facilitating deprotonation of –CH 2 in benzylamine. VO can not only adsorb and activate oxygen (O 2) but also capture plasmonic hot electrons, enhancing the forming of superoxide radical (O 2 −). Plasmonic hot holes assisted with O 2 − effectively achieve the selective oxidation of benzylamine. Finally, a possible synergetic mechanism combining the plasmon with the molecular activation is presented to illustrate the photocatalytic pathway at the molecular level. [ABSTRACT FROM AUTHOR]

[Display omitted] For semiconductor-based photocatalytic reactions, defect engineering has been proven as an efficient approach to enhance the photocatalytic performance. In this work, a synergistically PVP/EG-assisted in situ self-assembly strategy has been successfully developed for preparing flowerlike BiOCl nanospheres (NSP) assembled by ultrathin nanosheets (thickness of 3.8 nm) with abundant oxygen vacancies (OVs). During the hydrothermal process, PVP plays a template role in controlling the orientation of the crystallite growth, leading to the forming of nanosheets. Meanwhlie, ethylene glycol would induce the self-assembly of nanosheets into a loose hierarchical architecture duo to its stereo-hindrance effect. NSP achieves a twice higher photocatalytic conversion of benzylamine than BiOCl nanosheets (NST) under visible light. XPS, ESR, NH 3 -TPD results manifest that NSP possesses more active sites including OVs and unsaturated Bi atoms than NST, because of avoiding the accumulation of ultrathin nanosheets. In situ FTIR reveals that benzylamine molecules can be chemisorbed and activated on BiOCl interfaces via forming -N ... Bi- species. The OVs can facilitate the forming of superoxide radicals (•O 2 −), achieving the selective photooxidation. Finally, a possible synergetic mechanism based on the interaction of reactants and catalyst interfaces was proposed to illustrate the photocatalytic process at the molecular level. [ABSTRACT FROM AUTHOR]

A series of Fe-based MOFs MIL-68(Fe) with different defect contents were prepared and modulated by doping different amounts of Cu2+ ions for photocatalytic N 2 fixation by converting N 2 and H 2 O into NH 3 and O 2. [Display omitted] • MIL-68(Fe) with various OVs defect contents were prepared by Cu2+ doping for photocatalytic N 2 fixation. • Cu2+ doping induces crystal distortion to produce OVs defect and form coordinated unsaturated Fe2+ sites. • Coordinatively unsaturated Fe2+ sites can behave as active sites for the adsorption and activation of N 2. • Activated N 2 is reduced to NH 3 by the synergistic action of protonated hydrogen and photogenerated electrons. Photocatalytic N 2 fixation is a green process for ammonia synthesis by converting N 2 and H 2 O to NH 3 and O 2 directly using solar energy. Its efficiency is largely limited by the chemisorption and activation of N 2. This work adopts defect engineering strategy to develop a series of MIL-68(Fe) MOFs with varying concentrations of defects by doping Cu2+ on the metal nodes of MOFs. Upon Cu2+ doping, a larger number of oxygen vacancy defects are created due to the induced crystal distortion to form coordinatively unsaturated Fe2+ sites, which can serve as the active sites for promoting the chemisorption and activation of N 2. The photogenerated holes oxidize H 2 O to O 2 and H+, and the photogenerated electrons combine with formed H+ to reduce the activated N 2 to NH 3. It was found that the sample with 10 mol% Cu2+ doping shows the highest NH 3 production rate (21.0 μmol·g−1·h−1), which is 8.4 times higher than that (2.50 μmol·g−1·h−1) of the pristine MIL-68(Fe). The excellent performance is ascribed to the adequate Fe2+ active sites to chemisorb and activate N 2 and the optimal mobility of photogenerated charges. Finally, a mechanism is proposed to illustrate how the number of defects affects the photocatalytic N 2 fixation performance at the molecular level. [ABSTRACT FROM AUTHOR]