An iron-based metal–organic framework, MIL-101(Fe), promotes photocatalytic water oxidation to produce oxygen from aqueous silver nitrate solution under visible-light irradiation. The finely dispersed iron-oxo clusters embedded as nodes of the porous framework would contribute importantly to the efficient promotion of the reaction as compared to bulk hematite (α-Fe2O3).

The present article deals with Pt complex construction within Zr-based MOF having bipyridine units in the framework (Zr-MOF-bpy-PtCl2) and its photocatalytic activity for hydrogen production under visible-light irradiation (λ > 420 nm). Zr-MOF-bpy-PtCl2 is prepared by the construction of a Zr-based MOF using 2,2′-bipyridine-5,5′-dicarboxylic acid (Zr-MOF-bpy), and subsequent complexation reaction with K2PtCl4. XRD and N2 adsorption–desorption measurements have revealed that both Zr-MOF-bpy and Zr-MOF-bpy-PtCl2 have a UiO-type structure. From the results of UV–Vis and XAFS measurements, the incorporated Pt species has been proven to be in square planar geometry involving two N atoms and two Cl atoms as a result of the Pt coordination with bipyridine units in the framework. Zr-MOF-bpy-PtCl2 has been employed for a hydrogen production reaction from water containing a sacrificial electron donor under visible-light irradiation (λ > 420 nm). Zr-MOF-bpy-PtCl2 realizes steady hydrogen production, and the amount of evolved hydrogen reaches 8.3 μmol after the 9 h reaction period, while Zr-MOF-bpy exhibits no photocatalytic activity under the same conditions. It has also been found that the activity of Zr-MOF-bpy-PtCl2 is superior to that of the corresponding homogeneous complex analogue (bpy)PtCl2.

A Zr-based metal–organic framework with tetrakis(carboxyphenyl)porphyrin groups (Zr-MOF-TCPP: MOF-525) has been utilized as a photoredox catalyst to promote oxidative hydroxylation of arylboronic acids under green LED light irradiation. Zr-MOF-TCPP displays a superior catalytic activity for this process over the corresponding homogeneous catalyst (H4TCPP).

The present article describes the development of a periodic mesoporous organosilica (PMO)-based bifunctional catalyst that includes both oxidative and base catalytic activities. Periodic mesoporous ethylenesilica (PME) was selected as a catalyst support and modified with ethylenediamine through epoxidation of bridging ethylene moieties and the following nucleophilic addition in order to construct base sites. FT-IR measurements for the resulting material, PME-ED, reveal the successful introduction of amino groups into the bridging ethylene moieties. PME-ED can promote Knoevenagel condensation between benzaldehyde and various active methylene compounds as a solid base catalyst. The scope of applicable active methylene compounds in this catalytic system shows the base strength of PME-ED, in which a proton can be abstracted from diethyl malonate (pKa: 16.4) but not from benzyl cyanide (pKa: 21.9). Moreover, the generation of bifunctional catalytic properties to promote a one-pot tandem reaction consisting of alcohol oxidation and Knoevenagel condensation is realised by loading of Au nanoparticles within PME-ED. This catalyst design methodology can be also extended to developing another bifunctional catalyst that is composed of Pd nanoparticles and PME modified with N,N-dimethylethylenediamine in order to promote a Tsuji–Trost reaction.

A sequential one-pot reaction to produce organophosphorus compounds via Knoevenagel condensation and phospha-Michael addition has been realised by utilising ZIF-8 as a heterogeneous catalyst. The combination of 2-methylimidazolate anions and Zn2+ cations in ZIF-8 is revealed to be effective for the efficient promotion of the one-pot reaction.

A catalytically competent Cu species has been immobilized within the framework of a Zr-based metal–organic framework with bipyridine units, Zr-MOF-bpy, by a simple postsynthetic modification method from CuBr2 (Zr-MOF-bpy-CuBr2) and used for the selective oxidation of cyclooctene to cyclooctene oxide. Zr-MOF-bpy was synthesized by a simple solvothermal method and was shown to have a UiO-type structure. Diffuse reflectance UV–vis and XAFS measurements have revealed that the immobilized Cu species has a square-planar geometry of two N atoms and two Br atoms. Zr-MOF-bpy-CuBr2 catalyzed the selective oxidation of cyclooctene to cyclooctene oxide with high activity and selectivity in the presence of tert-butyl hydroperoxide as an oxidant. In addition, the catalytic ability of Zr-MOF-bpy-CuBr2 was demonstrated to be superior to that of the corresponding homogeneous catalyst ((bpy)CuBr2). It was also confirmed that Zr-MOF-bpy-CuBr2 can be reused as a heterogeneous catalyst without significant loss of its activity and selectivity.

A Ru complex-incorporated Ti-based MOF (Ti-MOF-Ru(tpy)2) has been synthesised by using a bis(4′-(4-carboxyphenyl)-terpyridine)Ru(II) complex (Ru(tpy)2) as an organic linker. Ti-MOF-Ru(tpy)2 promotes photocatalytic hydrogen production from water containing a sacrificial electron donor under visible-light irradiation up to 620 nm.

A novel one-pot reaction system is developed by utilizing a bifunctional metal–organic framework photocatalyst (Zr-MOF-NH2). Zr-MOF-NH2 promotes sequential photocatalytic oxidation and Knoevenagel condensation reaction to produce benzylidenemalononitrile from benzyl alcohol and malononitrile under UV-light irradiation.

An organoruthenium complex (–[biphRuCp]PF6–; biph = –(C6H4)2–, Cp = C5H5), constructed within a biphenylene-bridged inorganic–organic hybrid mesoporous material (HMM–biph) by use of a simple ligand-exchange reaction, has been used as a heterogeneous catalyst. UV–visible and X-ray absorption fine structure (XAFS) studies furnished evidence that the structure of the complex is closely similar to that of [(C6H6)RuCp]PF6, suggesting that the biphenylene moiety within HMM–biph directly coordinates the metal center of the organoruthenium complex. The –[biphRuCp]PF6– complex constructed within the HMM–biph (HMM–biphRuCp) catalyzes hydrosilylation of 1-hexyne with triethylsilane in a solid–gas heterogeneous system and gives α-vinylsilane as a main product. Moreover, HMM–biphRuCp has higher catalytic activity than the –[phRuCp]PF6– (ph = –C6H4–) complex constructed within phenylene-bridged HMM (HMM–phRuCp). The high catalytic performance of HMM–biphRuCp can be attributed to the high loading of the HMM–biph with the Ru complex, because of the electron-donating ability of the biphenylene moieties.

Efficient hydrogen production and photocatalytic reduction of nitrobenzene were achieved by using a Pt-deposited amino-functionalised Ti(IV) metal–organic framework (Pt/Ti-MOF-NH2) under visible-light irradiation. XRD and N2 adsorption measurements revealed that crystalline microporous structures were formed and maintained even after the Pt deposition. The photocatalytic activity for the visible-light-promoted hydrogen production was improved through the optimization of the deposition amount of Pt as a cocatalyst. The optimised amount of Pt was determined to be 1.5 wt%. The results of in situ ESR measurements clearly indicate that the reaction proceeds through the electron transfer from the organic linker to deposited Pt as a cocatalyst by way of titanium-oxo clusters. In addition, the Pt/Ti-MOF-NH2 photocatalyst was found to catalyse photocatalytic reduction of nitrobenzene under visible-light irradiation. It was also confirmed that the catalyst can be reused at least three times without significant loss of its catalytic activity.

Arenetricarbonyl metal complexes ([–phM(CO)3–] and [–biphM(CO)3–]; ph = phenylene, biph = biphenylene, M = Mo, Cr) constructed within Zr-based MOFs act as highly active and selective catalysts for epoxidation of cyclooctene. Catalytic activities of these complexes are enhanced with increasing the pore sizes of Zr-based MOFs.

The amino-functionalised metal–organic framework, MIL-101(Al)-NH2, has been synthesized by using a solvothermal method and employed as a bifunctional acid–base catalyst for a one-pot, sequential deacetalization–Knoevenagel condensation reaction. In preliminary studies, the abilities of MIL-101(Al)-NH2 to serve as an acid and base catalyst were explored separately by two typical acid- and base-catalysed reaction, that is, deacetalization of benzaldehyde dimethylacetal and Knoevenagel condensation of benzaldehyde with malononitrile. MIL-101(Al)-NH2 was found to catalyse each of these reactions with high efficiency. MIL-101(Al)-NH2 was then employed as a catalyst for the one-pot sequential deacetalization–Knoevenagel condensation reaction between benzaldehyde dimethylacetal and malononitrile. Benzylidenemalononitrile as the final product was successfully generated with a high yield via benzaldehyde over MIL-101(Al)-NH2. In addition, the catalytic ability of MIL-101(Al)-NH2 was demonstrated to be superior to those of conventional heterogeneous, homogeneous as well as other functionalised metal–organic framework catalysts. Finally, the results show that MIL-101(Al)-NH2 can be reused as a catalyst for this process without significant loss of its activity.

Visible light-responsive TiO2 (Vis-TiO2) electrode has been applied for the Pt-free separate-type photofuel cell (SPFC) where two different electrolytes containing various biomass derivatives and a I3−/I− redox solution were employed for the anode and cathode sides, respectively. This new SPFC exhibits good photoelectrochemical performance under simulated solar-light irradiation. It was found that the Rh3+ loading on Vis-TiO2 electrode enhanced the photoelectrochemical performance of the SPFC through the increase in the visible light absorption as well as the increase in the electron conductivity of Vis-TiO2 electrode.

Development of efficient Pt-free photofuel cells employing two different electrolytes containing various biomass derivatives and an I3−/I− redox solution for the anode and cathode sides, respectively, is described. These new, separate-type photofuel cells exhibit good photoelectrochemical performance under simulated solar-light irradiation.

Efficient hydrogen production and photocatalytic reduction of nitrobenzene were achieved by using a Pt-deposited amino-functionalised Ti(IV) metal–organic framework (Pt/Ti-MOF-NH2) under visible-light irradiation. XRD and N2 adsorption measurements revealed that crystalline microporous structures were formed and maintained even after the Pt deposition. The photocatalytic activity for the visible-light-promoted hydrogen production was improved through the optimization of the deposition amount of Pt as a cocatalyst. The optimised amount of Pt was determined to be 1.5 wt%. The results of in situ ESR measurements clearly indicate that the reaction proceeds through the electron transfer from the organic linker to deposited Pt as a cocatalyst by way of titanium-oxo clusters. In addition, the Pt/Ti-MOF-NH2 photocatalyst was found to catalyse photocatalytic reduction of nitrobenzene under visible-light irradiation. It was also confirmed that the catalyst can be reused at least three times without significant loss of its catalytic activity.

Arenetricarbonyl metal complexes ([–phM(CO)3–] and [–biphM(CO)3–]; ph = phenylene, biph = biphenylene, M = Mo, Cr) constructed within Zr-based MOFs act as highly active and selective catalysts for epoxidation of cyclooctene. Catalytic activities of these complexes are enhanced with increasing the pore sizes of Zr-based MOFs.

A Ru complex-incorporated Ti-based MOF (Ti-MOF-Ru(tpy)2) has been synthesised by using a bis(4′-(4-carboxyphenyl)-terpyridine)Ru(II) complex (Ru(tpy)2) as an organic linker. Ti-MOF-Ru(tpy)2 promotes photocatalytic hydrogen production from water containing a sacrificial electron donor under visible-light irradiation up to 620 nm.

A novel one-pot reaction system is developed by utilizing a bifunctional metal–organic framework photocatalyst (Zr-MOF-NH2). Zr-MOF-NH2 promotes sequential photocatalytic oxidation and Knoevenagel condensation reaction to produce benzylidenemalononitrile from benzyl alcohol and malononitrile under UV-light irradiation.

A Zr-based metal–organic framework with tetrakis(carboxyphenyl)porphyrin groups (Zr-MOF-TCPP: MOF-525) has been utilized as a photoredox catalyst to promote oxidative hydroxylation of arylboronic acids under green LED light irradiation. Zr-MOF-TCPP displays a superior catalytic activity for this process over the corresponding homogeneous catalyst (H4TCPP).

An iron-based metal–organic framework, MIL-101(Fe), promotes photocatalytic water oxidation to produce oxygen from aqueous silver nitrate solution under visible-light irradiation. The finely dispersed iron-oxo clusters embedded as nodes of the porous framework would contribute importantly to the efficient promotion of the reaction as compared to bulk hematite (α-Fe2O3).