The present review showcases the scientific progress in the field of dual-functional photocatalysis for hydrogen evolution coupled with the oxidation of chemical substances. Considering that hydrogen is a promising alternative to fossil fuels, photocatalytic water splitting represents an approach to produce hydrogen using abundant solar energy. However, the industrialization of this process has not occurred yet, mainly due to limitations related to the high cost, toxicity, poor stability, or low efficiency of the majority of the photocatalytic systems employed for water reduction. An approach to tackle these limitations is by taking advantage of the oxidative energy of the holes and by replacing the expensive and often toxic sacrificial electron donors with either organic pollutants (targeting their degradation) or organic substances that can be oxidized to added-value products. Following this 2-fold strategy, the production of sustainable hydrogen is accompanied by either the oxidative degradation of pollutants or the valorization of organic processes, in a single process. Herein, a detailed overview of the advancements in this dual-purpose field is offered, along with a discussion of the basic principles, the differences between similar fields, and how these can be distinguished. Although in its infancy, this dual-purpose technology has received radically increasing scientific interest over the past few years; this is expected, as the utilization of this approach can overcome multiple major environmental challenges, such as global warming, water scarcity, and pollution.

Herein, we first systematically studied the impact of different transition metalbased co-catalysts towards the photocatalytic water reduction, when they are physically mixed with the visible-light active MIL-125-NH2. All co-catalyst/MIL-125-NH2 photocatalytic systems were found to be highly stable after photocatalysis, with the NiO/MIL-125-NH2 and Ni2P/MIL-125-NH2 systems exhibiting high hydrogen (H2) evolution rates of 1084 and 1230 μmol h-1 g-1 , respectively. Secondly, we investigated how different electron donors affected the stability and H2 generation rate of the best Ni2P/MIL-125-NH2 system and found that triethylamine fulfils both requirements. We then replaced the electron donor with rhodamine

We showcase the key role of the co-catalyst when combined with MIL-125-NH2 towards the photocatalytic H2 generation.

We report the use of two earth abundant molybdenum sulfide-based cocatalysts, Mo3S132– clusters and 1T-MoS2 nanoparticles (NPs), in combination with the visible-light active metal–organic framework (MOF) MIL-125-NH2 for the photocatalytic generation of hydrogen (H2) from water splitting. Upon irradiation (λ ≥ 420 nm), the best-performing mixtures of Mo3S132–/MIL-125-NH2 and 1T-MoS2/MIL-125-NH2 exhibit high catalytic activity, producing H2 with evolution rates of 2094 and 1454 μmol h–1 gMOF–1 and apparent quantum yields of 11.0 and 5.8% at 450 nm, respectively, which are among the highest values reported to date for visible-light-driven photocatalysis with MOFs. The high performance of Mo3S132– can be attributed to the good contact between these clusters and the MOF and the large number of catalytically active sites, while the high activity of 1T-MoS2 NPs is due to their high electrical conductivity leading to fast electron transfer processes. Recycling experiments revealed that although the Mo3S132–/MIL-125-NH2 slowly loses its activity, the 1T-MoS2/MIL-125-NH2 retains its activity for at least 72 h. This work indicates that earth-abundant compounds can be stable and highly catalytically active for photocatalytic water splitting, and should be considered as promising cocatalysts with new MOFs besides the traditional noble metal NPs.

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A strategy for enhancing the photocatalytic performance of MOF-based systems (MOF: metal−organic framework) is developed through the construction of MOF/ MOF heterojunctions. The combination of MIL-167 with MIL-125-NH 2 leads to the formation of MIL-167/MIL-125-NH 2 heterojunctions with improved optoelectronic properties and efficient charge separation. MIL-167/MIL-125-NH 2 outperforms its single components MIL-167 and MIL-125-NH 2 , in terms of photocatalytic H 2 production (455 versus 0.8 and 51.2 μmol h −1 g −1 , respectively), under visible-light irradiation, without the use of any cocatalysts. This is attributed to the appropriate band alignment of these MOFs, the enhanced visible-light absorption, and long charge separation within MIL-167/MIL-125-NH 2 . Our findings contribute to the discovery of novel MOF-based photocatalytic systems that can harvest solar energy and exhibit high catalytic activities in the absence of cocatalysts.

Herein, we explored a simple metal-organic framework (MOF) mediated synthesis for the controlled preparation of pure and mixed phase titania (TiO2) nanoparticles. Scanning electron microscopy images revealed that the MOF-derived TiO2 retain the MOF crystal shape, and through powder X-ray diffraction and X-ray photoelectron spectroscopy, it is demonstrated that the crystal-template is composed of nanosized TiO2 rutile and anatase particles. The presence of both TiO2 rutile and anatase phases in the crystal-template enhances the interactions between them, thus suppressing the electron-hole recombination. This has an impact toward the photocatalytic reduction of water as the templated MOF-derived TiO2 outperforms the commercial (P25 Degussa), titanium isopropoxide-derived and non-templated MOF-derived TiO2. Our study demonstrates that the morphologicallyinduced high charge separation efficiency afforded by using MOF crystals as precursors can lead to the generation of catalytically more active materials that can challenge existing photocatalysts in the field of hydrogen generation.

The photo-active MIL-125 and MIL-125-NH 2 metal−organic frameworks (MOFs), despite having a very similar crystalline structure, exhibit different optical behaviors. Luminescence in MIL-125 decays in about 1 ns, while for its amino counterpart, the lifetime of charge carriers is at least 1 order of magnitude larger. The origin of this difference is the key element for understanding the photocatalytic behavior of MIL-125-NH 2 when associated with active nanoparticles, a behavior that is completely absent in MIL-125. By performing advanced ab initio electronic structure calculations, we find that charge carriers interact differently in the two MOFs with subsequent effects on the luminescence lifetimes and their catalytic performances. To confirm the predictions of our model, we synthesized a novel material in the MIL-125 family, MIL-125-NH 2 -[10%](OH) 2 , and confirm that our theory correctly predicts a faster decay compared to MIL-125-NH 2 .