The development of MOF-based efficient and reusable catalysts for hydrogen production under simulated sunlight irradiation, especially through overall water splitting, remains challenging. This is mainly due to either the inappropriate...

The photochemistry of two isostructural metal-organic frameworks based on 5-amino/5-formamidoisophthalate (CAU-10-NH2 /NHCHO) or mixed-linker 5-amino/5-formamido- and 5-nitroisophthalate (CAU-10-NO2 /NH2 /NHCHO) has been studied using laser flash photolysis. 355 nm excitation of CAU-10-NH2 /NHCHO leads to a transient absorption spectrum characterized by a broad continuous absorption from 380 to 800 nm that was attributed to the presence of holes (440 nm) and electrons (600 nm) based on iPrOH and N2 O quenching, respectively. In contrast, no transients were observed for the isostructural mixed-linker CAU-10-NO2 /NH2 /NHCHO, data that is compatible with the uniform distribution of linkers 5-amino/5-formamido/5-nitroisophthalate as charge-transfer complex pairs. The same effect of quenching of 5-aminoisophthalate transients by 5-nitroisophthalate was also observed in aqueous solution (pH 9) but with much lower strength. Using a simple Stern-Volmer formalism allowed the estimation of the interaction of 5-aminoisophthalate with 5-nitroisophthalate in MOF to be 5.2×10(4) times stronger than in the aqueous phase.

A series of (N, O)-co-doped graphenes with different N and O loadings are prepared by the pyrolysis of natural chitosan. When the percentage of dopant increases, the conduction-band potential and charge-separation quantum yield increase, whereas the charge-separation lifetime decreases.

Room temperature synthesis (RTS) of tetravalent MOFs is a promising strategy to design MOFs and their related (nano)composites. By employing these mild conditions, herein, we report for the first time an efficient sustainable way to form highly redox active Ce(IV)-MOFs that are inaccessible at elevated temperatures. Consequently, not only highly crystalline Ce-UiO-66-NH2 is synthesized, but also many other derivatives and topologies (8 and 6-connected phases) without compromise in space-time yield. Their photocatalytic HER and OER activity under simulated sunlight irradiation are in good agreement with their energy level diagrams: Ce-UiO-66-NH2 and Ce-UiO-66-NO2 are the most active photocatalysts for the HER and OER, respectively, with a higher activity than other metals-based UiO-type MOFs. Combining Ce-UiO-66-NH2 with supported Pt NPs results finally in one of the most active and reusable photocatalysts for the overall water splitting into H2 and O2 under simulated sunlight irradiation, due to its efficient photoinduced charge separation evidenced by laser flash photolysis and photoluminescence spectroscopies.

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