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The activation capacity of molecular oxygen is an important indicator to evaluate the photocatalytic efficiency of photocatalysts. In this paper, WS2 nanosheet was deposited on hyper-crosslinked CTF-1-G (obtained by molecular expansion from covalent triazine framework CTF-1) to form a C-GW heterojunction, which promoted the photodegradation of pollutants and the activation of molecular oxygen. This novel C-GW heterojunction exhibited excellent degradation property for organic pollutants (tetracycline (TC), rhodamine B (RhB)) and activating molecular oxygen under visible light irradiation. Among them, C-GW15 could degrade 98% of 20 ppm TC in 60 min and 99% of 30 ppm RhB in 30 min, and it had the highest hydrogen generation rate and hydrogen production amount in 4 hours, which were 8.74 mmol h−1 g−1 and 34.94 mmol g−1, respectively. Meanwhile, C-GW15 had the strongest 3,3′,5,5′-tetramethylbenzidine oxidation capacity and could generate 1.83 μmol of ˙O2− in 60 min and the production of H2O2 was 20.8 μmol L−1 in 40 min. The results of this study clearly indicated that the combination of WS2 and CTF-1-G can enhance the visible light absorption capacity and photogenerated carrier separation efficiency, thus promoting the photocatalytic performance. Finally, a Z-type photocatalytic mechanism was proposed based on radical capture, molecular oxygen activation experiments and electron spin resonance analysis. These findings will extend the fundamental understanding of the Z-type photocatalytic mechanism and provide new opportunities for the rational design of CTF heterojunctions for the treatment of environmental pollution and clean energy conversion. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) have great potential for producing photoelectrocatalyzed hydrogen and degrading pollutants, owing to several factors such as high porosity and tunable semiconductor-like properties. Wide band gaps, which restrict their use to only UV light induced reactions, and low efficiencies for the separation of photogenerated charge carriers (electrons and holes) pose significant challenges to the widespread applications of MOFs. In this study, a hierarchical hollow Pt@H-UiO-66-NH2/CdS ternary catalyst was designed and synthesized. The immobilized CdS nanoparticles (NPs) in this catalyst endow the MOF H-UiO-66-NH2 with high visible light absorption ability and the Pt NPs serve as electron sinks to improve charge carrier separation. Furthermore, the hierarchical hollow structure of H-UiO-66-NH2 in the composite contributes to boosting light absorption and shortening the distance for charge transfer. As a proof of principle, Pt@H-UiO-66-NH2/CdS catalyzes methylene blue (MB) degradation with a high rate constant of 1.025 × 10−2 and hydrogen production with a rate of 12 810 μmol g−1 h−1, the latter of which is about 2.3, 11.7 and 173 times higher than those of Pt@UiO-66-NH2/CdS, H-UiO-66-NH2/CdS and Pt@H-UiO-66-NH2, respectively. [ABSTRACT FROM AUTHOR]

Self-doping by Ti3+ is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti3+-doped TiO2 seems to be a challenge due to the easy oxidation of Ti3+ during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti3+-doped TiO2, in which both the Ti3+ and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti3+-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti3+ in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response. [ABSTRACT FROM AUTHOR]