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A 1,10-phenanthroline-based periodic mesoporous organosilica (Phen-PMO) with an ordered 2-D hexagonal mesoporous structure was synthesized by co-condensation of 3,8-bis[(triisopropoxysilyl)methyl]-1,10-phenanthroline and BTEE.

The rapid detection of biomolecules greatly contributes to health management, clinical diagnosis, and prevention of diseases. Mass spectrometry (MS) is effective for detecting and analyzing various molecules at high throughput. However, there are problems with the MS analysis of biological samples, including complicated separation operations and essential pretreatments. In this study, a nanostructured organosilica substrate for laser desorption/ionization mass spectrometry (LDI-MS) is designed and synthesized to detect peptides and small proteins efficiently and rapidly. The surface functionality of the substrate is tuned by perfluoroalkyl/alkylamide groups mixed at a molecular level. This contributes to both lowering the surface free energy and introducing weak anchoring sites for peptides and proteins. Analyte molecules applied onto the substrate are homogeneously distributed and readily desorbed by the laser irradiation. The organosilica substrate enables the efficient LDI of various compounds, including peptides, small proteins, phospholipids, and drugs. An amyloid β protein fragment, which is known as a biomarker for Alzheimer's disease, is detectable at 0.05 fmol μL

We synthesized a novel periodic mesoporous organosilica (PMO) containing pyridinylethynylpyridine (PEPy) as a molecular recognition host material. Catechol guests were specifically adsorbed on the PEPy moieties of the PMO surface.

Organosilica materials can be synthesized via sol–gel polycondensation of organosilanes under acidic or basic conditions, although the cleavage of Si–C bonds in the arylsilane precursors is a major challenge. The present study investigated three practical strategies for suppressing Si–C bond cleavage of arylsilanes, using quantum chemical calculations. These were: (i) changing the position of the silyl group on the aromatic ring, (ii) inserting alkyl linkers into the Si–C bond, and (iii) removing metal ions from the organosilane ligands. Building on prior work, the stabilities of key intermediates in the Si–C cleavage reaction were numerically evaluated by calculating proton affinity (PA) values, and the effects of structural modifications of the arylsilanes were explored. With respect to strategy (i), the calculated PA values demonstrate that the stability of the Si–C bond is dependent on both the position of the silyl group and the reaction conditions. In the case of strategy (ii), the effects of incorporating (CH2)m linkers (m = 1–3) were examined. The results suggest that the insertion of (CH2)m with m ≥ 2 could potentially suppress Si–C cleavage under basic conditions. With respect to strategy (iii), the coordination of bipyridine organosilane precursors to metal ions was found to greatly affect PA values. The results suggest that metal ions in the reaction solution could possibly promote Si–C cleavage under basic conditions.

Zinc acetate (Zn(OAc)2) was successfully immobilized on a bipyridine-based periodic mesoporous organosilica (BPy-PMO-TMS), as confirmed by solid-state NMR and energy-dispersive X-ray spectroscopies, X-ray diffractometry, and nitrogen adsorption/desorption isotherm analyses. The immobilized Zn complex, Zn(OAc)2(BPy-PMO-TMS), exhibited good catalytic activity during the N-formylations of amines and amides with CO2 and PhSiH3 to produce the corresponding formamides. Zn(OAc)2(BPy-PMO-TMS) with a lower Zn loading was found to exhibit higher catalytic activity.

Over the past few decades, a number of homogeneous transition metal complex catalysts for efficient organic transformations have been developed. Some of these highly active catalysts have been desi...

Nanoimprinting methods have been used widely to prepare various patterned or nanostructured thin films from inorganic or organic components. However, the accumulation of large functional aromatic groups in covalently crosslinked nanoimprints is challenging, due to the difficulty in controlling the fluidity and reactivity of the precursor films. In this work, nanoimprinting of naphthalimide-silica sol-gel films results in vertically oriented nanoporous structures consisting of covalently crosslinked UV-absorbing frameworks. The nanoimprinted films demonstrate potential as robust analytical substrates for laser desorption/ionization mass spectrometry (LDI-MS). The sol-gel polycondensation behavior of the precursors is examined using 29Si NMR spectroscopy to determine reaction conditions suitable for nanoimprinting. The inorganic-organic hybrid frameworks containing a high density of naphthalimide groups exhibit small volume shrinkage during the polycondensation reactions, which leads to desired nanoimprinting. Various bio-related compounds on the order of picomole to femtomole quantities are detectable by LDI-MS measurements using the nanoimprinted substrates. To improve their user-friendliness and signal intensity in LDI-MS analysis, the nanoimprinted substrates are patterned with surface-modified silica nanoparticles. The direct formation of surface nanostructures by nanoimprinting of functional organosilica films may open a new path to developing optically and electronically functional materials, thereby widening their utility.

Low-lying singlet excited states of pyrene derivatives originated from the 1La and 1Lb states of pyrene have decisive influences on their absorption and fluorescence emission behaviors. Calculation of these excited states with quantitative accuracy is required for the theoretical design of pyrene derivatives tailored to target applications; this has been a long-standing challenge for ab initio quantum chemical calculations. In this study, we explore an adequate computational scheme through calculations of pyrene and its phenyl-substituted derivatives using multi-reference perturbation theory (MRPT) methods. All valence π orbitals on the pyrene moiety were assigned to the active orbitals. Computational load was reduced by restricting the electron excitations within the active orbitals in the preparation of reference configuration space. A generalized multi-configuration quasi-degenerate perturbation theory (GMCQDPT) was adopted to treat the reference space other than the complete active space. The calculated 1La and 1Lb excitation energies of pyrene are in good agreement with the experimental values. Calculations of 1,3,6,8-tetraphenyl pyrene suggest that the energetic ordering of 1La and 1Lb is inverted through tetraphenyl substitution and its lowest singlet excited state is the 1La parentage of pyrene, which is consistent with the experimentally deduced scheme. These results are not readily obtained by MRPT calculations with a limited number of active orbitals and single-reference theory calculations. Diphenyl pyrenes (DPPy) were also calculated at the same level of theory to investigate the dependence on the substitution positions of phenyl groups.

Periodic mesoporous organosilicas (PMOs) were synthesized from precursor mixtures of bridged organosilanes containing various ratios of divinylbenzene (vPh) and divinylpyridine (vPy) under basic conditions. The bifunctional vPh-vPy-PMOs exhibited ordered mesoporous structures and molecular scale periodicity to form crystal-like pore walls. With an increase in the vPy content, the diffraction peak due to the molecular-scale periodicity was gradually shifted from 14.75° to 14.95° along with a gradual change in external morphology of the PMO particles from spherical to rod-like shapes. Moreover, the fluorescence from vPh was largely quenched by vPy in vPh-vPy-PMOs compared to the physical mixtures of vPh-PMO and vPy-PMO. These results strongly suggest that the vPh and vPy units were homogeneously distributed within the PMO framework. To the best of our knowledge, this is the first study to demonstrate the homogeneous distribution of different organic bridges in multifunctional PMOs.

The combined use of a metal-complex catalyst and an enzyme is attractive, but typically results in mutual inactivation. A rhodium (Rh) complex immobilized in a bipyridine-based periodic mesoporous organosilica (BPy-PMO) shows high catalytic activity during transfer hydrogenation, even in the presence of bovine serum albumin (BSA), while a homogeneous Rh complex exhibits reduced activity due to direct interaction with BSA. The use of a smaller protein or an amino acid revealed a clear size-sieving effect of the BPy-PMO that protected the Rh catalyst from direct interactions. A combination of Rh-immobilized BPy-PMO and an enzyme (horse liver alcohol dehydrogenase; HLADH) promoted sequential reactions involving the transfer hydrogenation of NAD+ to give NADH followed by the asymmetric hydrogenation of 4-phenyl-2-butanone with high enantioselectivity. The use of BPy-PMO as a support for metal complexes could be applied to other systems consisting of a metal-complex catalyst and an enzyme.

The development of synthetic methods and reaction systems for safe radical reactions is of extremely industrial importance. Here we proposed new concept for a safe radical reaction system based on combined use of a mesoporous catalyst and an insoluble solid scavenger. We selected Mukaiyama epoxidation of olefin as a model radical reaction and investigated the catalysis of Cu-bipyridine complexes immobilized on trimethylsilylated bipyridine-periodic mesoporous organosilica as a solid support. The immobilized Cu complex exhibited high catalytic activity and reusability for Mukaiyama epoxidation at low substrate concentration (1 mmol) but free-radical auto-oxidation also occurred at high substrate concentration (7 mmol). Although both epoxidation reactions outside and inside the mesochannels were almost completely quenched by addition of molecular scavenger, addition of solid scavenger allowed quenching the reaction outside the mesopores but not inside the mesopores because the solid scavenger could not access the interior of the mesochannels. Thus, the combined use of a mesoporous catalyst and a solid radical scavenger would offer new reaction system for safe radical reactions.

Bipyridine periodic mesoporous organosilica (BPy-PMO) is a porous material in which the pore walls consist of silica frameworks bridged by 2,2′-bipyridine (bpy) functional groups, and is expected to be a novel platform for catalysts and photocatalysts. Metal complexes formed on the pore surfaces of BPy-PMO are under unusual environmental conditions that are entirely different from those in the bulk solids or in solution. To understand the effects of the unique structural features of the pore surfaces on the metal complexes, this study focused on the combination of BPy-PMO with Re(bpy)(CO)3Cl (Re-BPy-PMO) and analyzed the metal-to-ligand charge transfer (MLCT) absorption band of this material. UV/vis and infrared analyses demonstrated that the Re-complex in Re-BPy-PMO interacts with water molecules adsorbed on the pore surfaces. Quantum chemical calculations suggest that the Re-complex also interacts with SiOH groups on the silica framework. Combined interactions are responsible for the unexpectedly short MLCT absorption wavelength of Re-BPy-PMO. This hypothetical mechanism is consistent with a red shift of the MLCT absorption following trimethylsilylation, which transforms SiOH groups to SiOSiMe3 (TMS) groups and removes adsorbed water. Calculations also suggest that the TMS group is more electron-donating than the SiOH group. Therefore, the trimethylsilylation should result in a blue shift of the MLCT absorption with regard to the substituent effect, which is inconsistent with the experimental observations. Evidently, the effect of the removal of water and SiOH groups is sufficiently powerful to counteract the blue shift. Thus, the pore-surface features have a significant influence on the metal complex.

The utility of a bipyridine periodic mesoporous organosilica, BPy-PMO, as a support material of a hydrosilylation catalyst was investigated in the hydrosilylation of phenylacetylene with trimethoxysilane. [PtMe2(BPy-PMO)] (1) exhibited a moderate catalytic activity, whereas the reaction was successfully catalysed by [PtMe2(BPy-PMO-TMS)] (2) bearing end-capped TMS groups on the surface. Spectroscopic analyses of 2 revealed that the porous structure of BPy-PMO-TMS remained almost unchanged through the reaction. The hot filtration test supported the nonleaching property of 2, thereby exhibiting good reusability without the loss of the product yields.

2,2'-Bipyridine is the most widely used chelating ligand for developing metal complexes in coordination and supramolecular chemistry. Here, we present a series of three bipyridine periodic mesoporous organosilicas (BPy-PMOs) grafted with lanthanide β-diketonate complex for the purpose of obtaining thermochromic materials, which can be employed as ratiometric temperature sensors. Such thermometers are based on the ratio of two emission intensity peaks and are not affected by factors such as alignment or optoelectronic drift of the excitation source and detectors. Three thermometric systems are studied: Dy-Dy, Tb-Sm, and Tb-Eu with the first two showing very attractive performance. For the first two systems, some of the best reported to date relative sensitivities are observed. In the BPy-PMO@Dy(acac)3 system, it is very unusual that the 4I15/2→ 6H15/2 transition is already occupied at low temperature such as 200 K, which influences its thermometric behavior. The Tb-Sm shows excellent performance in the physiological range and when suspended in water. We have additionally confirmed that the BPy-PMO hybrid materials lack toxicity to human cells, proving them very promising candidates for biomedical thermometric applications.

A periodic mesoporous organosilica (PMO) containing 2,2′-bipyridine groups (BPy-PMO) has been shown to possess a unique pore wall structure in which the 2,2′-bipyridine groups are densely and regularly packed. The surface 2,2′-bipyridine groups can function as chelating ligands for the formation of metal complexes, thus generating molecularly-defined catalytic sites that are exposed on the surface of the material. We here report the construction of a heterogeneous water oxidation photocatalyst by immobilizing several types of tris(2,2′-bipyridine)ruthenium complexes on BPy-PMO where they function as photosensitizers in conjunction with iridium oxide as a catalyst. The Ru complexes produced on BPy-PMO in this work were composed of three bipyridine ligands, including the BPy in the PMO framework and two X2bpy, denoted herein as Ru(X)-BPy-PMO where X is H (2,2′-bipyridine), Me (4,4′-dimethyl-2,2′-bipyridine), t-Bu(4,4′-di-tert-butyl-2,2′-bipyridine) or CO2Me (4,4′-dimethoxycarbonyl-2,2′-bipyridine). Efficient photocatalytic water oxidation was achieved by tuning the photochemical properties of the Ru complexes on the BPy-PMO through the incorporation of electron-donating or electron-withdrawing functionalities. The reaction turnover number based on the amount of the Ru complex was improved to 20, which is higher than values previously obtained from PMO systems acting as water oxidation photocatalysts.

A diiron [FeFe]-hydrogenase model complex tethered with a maleimide group, FeFe1, was covalently grafted on the pore surface of a periodic mesoporous organosilica with thiol groups (SH-PMO) to form an efficient heterogeneous hydrogen (H-2)-evolution catalyst FeFe1@PMO. The coordination structure of the FeFe1 complex and the ordered pore structure were almost completely preserved even after immobilization of FeFe1 on SH-PMO. The FeFe1@PMO promoted photocatalysis for H-2 evolution in water containing a photosensitizer [Ru(bpy)(3)](2+), with a turnover number (TON) of 310 over 120 min. The TON was greater than those of an analogous homogeneous FeFe1 catalyst (TON=180) and conventional diiron complexes immobilized on solid supports (TON=6-18). The increased TON for FeFe1@PMO compared to the homogeneous FeFe1 was attributed to the improvement in the stability of the FeFe1 complex by immobilization on the pore surface of SH-PMO. A [Ru(bpy)(3)](2+) photosensitizer tethered with a maleimide (Ru1) was prepared and co-immobilized on FeFe1@PMO to form an all-solid-state photocatalyst FeFe1-Ru1@PMO. FeFe1-Ru1@PMO evolved H-2 without the additional [Ru(bpy)(3)](2+) photosensitizer, suggesting efficient photoinduced electron transfer from the immobilized Ru1 to the immobilized FeFe1.

Mass spectrometry (MS) is a powerful analytical tool that can detect and identify multiple kinds of compounds such as biomolecules with high sensitivity. Recently, various nanoporous solid substrates have been developed for organic-matrix-free laser desorption/ionization (LDI) of analytes. In this study, periodic mesoporous organosilica (PMO) films are demonstrated for the first time to be promising as solid substrates for LDI mass spectrometry (LDI-MS). UV-absorbing PMO thin films having surface open pores with diameters of 20–30 nm are prepared using a triphenylamine derivative as a precursor and an amphiphilic block copolymer as a structure-directing template, followed by nanoscale surface etching. Peptide analytes introduced into the mesopores can be efficiently detected on the order of sub-picomole without the addition of an organic matrix. In addition, the PMO film shows an advantage of superior shot-to-shot reproducibility compared to a conventional matrix-assisted LDI (MALDI) method on a simple and easy way. PMO films with high tunability of framework composition and functionality may pave the way to new solid substrates for LDI-MS.

The dichlorodioxomolybdenum(VI) complex (MoO2Cl2) is an efficient and low-cost homogeneous catalyst for a variety of organic reactions, but its activity usually decreases after immobilization on a solid support. This report describes the synthesis of heterogeneous Mo complex catalysts using a bipyridine-periodic mesoporous organosilica (BPy-PMO) as a solid chelating ligand and MoO2Cl2 as a precursor, and their catalysis in the epoxidation of olefins with tert-butyl hydroperoxide (TBHP). The MoO2Cl(OH) complex could be immobilized on trimethylsilylated BPy-PMO (BPy-PMO-TMS), which was confirmed by Fourier-transform infrared spectroscopy, Raman spectroscopy, and X-ray absorption fine-structure analysis. The Mo complex immobilized on BPy-PMO-TMS exhibited greater catalytic activity for the epoxidation of cis-cyclooctene compared with conventional heterogeneous Mo complex catalysts using mesoporous silica, polystyrene, and naked BPy-PMO as supports. A large amount (up to 0.72 mmol g–1) of the Mo complex could...

This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO)3 Cl] immobilized on a bipyridine-periodic mesoporous organosilica (BPy-PMO) acting as a solid support. The immobilized Re complex generated a metal-to-ligand charge transfer absorption band at 400 nm. This wavelength is longer than that exhibited by Re(bpy)(CO)3 Cl in the polar solvent acetonitrile (371 nm) and is almost equal to that in nonpolar toluene (403 nm). The photocatalytic activity of this heterogeneous Re complex was lower than that of a homogeneous Re complex due to the reduced phosphorescence lifetime resulting from immobilization. However, the catalytic activity was enhanced by the co-immobilization of the ruthenium (Ru) photosensitizer [Ru(bpy)3 ]2+ on the PMO pore surfaces. Quantum chemical calculations suggest that electron transfer between the Ru and Re complexes occurs through interactions between the molecular orbitals in the pore walls. These results should have applications to the design of efficient heterogeneous CO2 reduction photocatalysis systems.

Transfer hydrogenation of unsaturated nitrogen heterocycles using a rhodium catalyst immobilized on bipyridine-periodic mesoporous organosilica (BPy-PMO) is described. The immobilized catalyst was prepared by mixing [Cp*RhCl2]2 (Cp* = η5-C5Me5) with BPy-PMO powder in DMF at 60 °C and characterized by nitrogen adsorption measurements, solid-state NMR spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. In the presence of the catalyst, a wide variety of unsaturated nitrogen heterocycles underwent transfer hydrogenation to afford the corresponding products in good yields. The immobilized catalyst could be readily recovered by centrifugation and reused several times in the transfer hydrogenation process., ファイル公開：2019/01/21

Outline Highlights Abstract Graphical abstract Keywords 1. Introduction 2. Experimental 3. Results and discussion 4. Conclusions References Show full outline Figures (9) Unlabelled figure Scheme 1. Formation of Au complex on BPy-PMO Fig. 1. (a) Au L3-edge XANES, (b) EXAFS oscillation, (c) Fourier transforms of EXAFS Fig. 2. (a) N2 adsorption isotherms and (b) NLDFT pore diameter distribution curves of Fig. 3. XRD patterns of BPy-PMO (black line) and AuNPs/BPy-PMO (blue line) in (a) low Fig. 4. (a) N2 adsorption isotherms and (b) XRD patterns of bare (black line) and Show all figures Elsevier Catalysis Today Volume 298, 1 December 2017, Pages 258-262 Catalysis Today Facile formation of gold nanoparticles on periodic mesoporous bipyridine-silica Silica-supported gold nanoparticles (AuNPs) can be synthesized on a bipyridine incorporated periodic mesoporous organosilica (BPy-PMO) as an inorganic support. Reaction of a bipyridine group in the periodic mesoporous organosilica with HAuCl4 forms an AuCl2-based complex, and its structure corresponds to a homogeneous complex, [AuCl2(bpy)]Cl. Thermal reduction of the complex in H-2 results in the formation of small gold nanoparticles with an average size of ca. 3.8 nm. Combined with nitrogen adsorption, XRD, UV/Vis, TEM, and XAFS measurements, it is demonstrated that uniform gold nanoparticles are homogeneously distributed inside mesopores. The size and distribution of gold nanoparticles are mainly controlled by strong interaction of surface metallic Au with pore walls of the periodic mesoporous organosilica. AuNPs/BPy-PMO shows higher catalytic activity than Au/MCM-41 in aerobic oxidation of benzaldehyde. (C) 2017 Elsevier B.V. All rights reserved.

Photocatalytic H2 production from water is one approach to solving global energy problems. Much attention has been paid to the promising applications of solid-state molecular photocatalysts because of their ease of handling, recyclability, and designable catalytic properties. We report an efficient photocatalytic H2 evolution system using methylacridone (MeAcd)-bridged periodic mesoporous organosilica (MeAcd-PMO), which has visible light absorption and electron-donating properties. MeAcd-PMO loaded with Pt nanoparticles efficiently generated H2 under visible light irradiation with a high apparent quantum yield (8.6% at 400 nm). Transient absorption measurements revealed a unique light-harvesting mechanism involving the excitation energy migration of the lowest singlet excited state on the MeAcd-PMO framework, which has not been observed in conventional solid-state molecular photocatalysts. MeAcd-PMO exhibiting this energy migration behavior is expected to be useful as a host material for constructing efficient photocatalytic systems which mimic natural photosynthesis

We report size-controllable syntheses of spherical coordination polymer particles using only K2[Pt(CN)4], Zn(NO3)2·6H2O, and water, and their conversion to Pt-ZnO composite and PtZn alloy. This method can control both the size and surface morphology of coordination polymer particles by changing the concentrations of the starting materials without any organic solvents, surfactants, and heating treatment. For example, the increasing of [Pt(CN)4]2− concentration reduced the particle size and improved the smoothness of particle surface. Thermal treatment of the particles in oxidative atmosphere at 500 °C results in the formation of Pt-ZnO composite. Upon further treatment in reducing atmosphere at 400 °C, the composite was converted to PtZn alloy compound. After conversion to composite and alloy, the initial particle size and surface morphology were retained.

To understand the excited-state dynamics of Ph moieties in a framework of the phenylene–silica nanotube (Ph-NT), temperature and time dependence of the fluorescence were investigated. The time dependence of the Ph exciton fluorescence and excimer fluorescence was successfully analyzed by the model including the diffusion of the Ph excitons and their subsequent trapping at the defect center and the excimer sites. The energy migration of the Ph exciton in the Ph-NT is suggested similarly to phenylene-bridged periodic mesoporous organosilica (Ph-PMO) powder with crystal-like wall structure, although X-ray diffraction of Ph-NT indicates less molecular-level periodicity of Ph moieties in the framework of the nanotube. The excited-state dynamics of Ph moieties in Ph-NT will be discussed by comparing that of Ph-PMO.

A periodic mesoporous organosilica (PMO) containing 2,2'-bipyridine (bpy) ligands within the framework (BPy-PMO) has great potential for designing novel catalysts by modifying metal complexes. A photosensitizing site (Ru(PS)) was introduced by treating cis-[Ru(bpy)2 (dimethylsulfoxide)Cl]Cl with BPy-PMO. Then a catalytic site (Ru(Cat)) was brought in Ru(PS)x -BPy-PMO by reaction with a ruthenium polymer [Ru(CO)2 Cl2 ]n . The stepwise modification of BPy-PMO successfully affords a novel photocatalyst Ru(PS)x -Ru(Cat)y -BPy-PMO. The molar fractions (x, y) of Ru(PS) and Ru(Cat) were determined by energy dispersive X-ray (EDX) measurement and quantification of the amount of CO emitted in the photo-decarbonylation of Ru(Cat), respectively. Photochemical CO2 reduction (λex >430 nm) by Ru(PS)x -Ru(Cat)y -BPy-PMO in a CO2 -saturated N,N-dimethylacetamide/water solution containing 1-benzyl-1,4-dihydronicotinamide catalytically produced CO and formate. The total turnover frequency of CO and formate reached more than 162 h-1 on x=0.11 and y=0.0055. The product selectivity (CO/formate) became large when the ratio of Ru(PS)-to-Ru(Cat) (x/y) was increased. The photocatalysts can be recycled at least three times without losing their catalytic activity, demonstrating that the Ru(PS) and Ru(Cat) units were strongly immobilized on the BPy-PMO framework.

Heterogeneous metal complex catalysts for the water oxidation reaction have ever been desired for the development of devices simulating photosynthesis. This paper describes the design of highly active and robust heterogeneous iridium complex catalysts for chemical water oxidation. The heterogeneous catalyst (Ir-BPy-NT) was prepared by the post-synthetic metalation of bipyridine-containing mesoporous organosilica nanotubes (BPy-NT) with an [IrCp*Cl(μ-Cl)]2 (Cp* = η5-pentamethylcyclopentadienyl) complex. The as-prepared Ir-BPy-NT catalyst showed enhanced durability with high reaction activity compared to the analogous homogeneous and the conventional heterogeneous ones, due to the stable nanotube structures as well as the isolated active sites. The unique one-dimensional nanotubes with large pore diameters can also reduce the diffusion limitation and facilitate the transport of reactants and products during reactions.

Periodic mesoporous organosilicas (PMOs) represent a new class of hybrid organic–inorganic porous materials, in which organic groups are densely and covalently embedded within the pore walls in the framework of the base material. PMOs have the distinct advantage of allowing various functional groups to be integrated into the pore walls via the appropriate selection of organic precursors, and also allow tuning of the spatial arrangement of such moieties within the framework. This chapter describes the synthesis of PMOs with various structures and organic functionalities, as well as the use of these materials in diverse applications, including light-harvesting antennae, heterogeneous molecular photocatalysts, photovoltaic devices, and as substrates for laser desorption/ionization mass spectrometry and solid supports for heterogeneous metal complex catalysis.

CO-free hydrogen production from methanol and water, using transition metal complex catalysts, has attracted increasing attention. However, liquid-phase batch reactions using homogeneous catalysts are impractical for large-scale operations owing to the consumption of bases and the use of organic solvents or additives. Herein, we report a novel method for continuous hydrogen production from a simple methanol-water solution under vapor-phase flow. The reaction was catalyzed by an anionic iridium-bipyridonate (Ir-bpyd) complex immobilized on a periodic mesoporous organosilica. Liquid-phase batch reaction using homogeneous anionic Ir-bpyd complex was immediately deactivated due to CO 2 generation, whereas no catalyst deactivation was observed in the vapor-phase flow reaction because CO 2 was smoothly removed from the catalyst bed, enabling continuous hydrogen production without the addition of a base. Thus, the critical problems pertaining to homogeneous catalysts were successfully overcome.

Artificial photosynthesis-reduction of CO2 into chemicals and fuels with water oxidation in the presence of sunlight as the energy source-mimics natural photosynthesis in green plants, and is considered to have a significant part to play in future energy supply and protection of our environment. The high quantum efficiency and easy manipulation of heterogeneous molecular photosystems based on metal complexes enables them to act as promising platforms to achieve efficient conversion of solar energy. This Review describes recent developments in the heterogenization of such photocatalysts. The latest state-of-the-art approaches to overcome the drawbacks of low durability and inconvenient practical application in homogeneous molecular systems are presented. The coupling of photocatalytic CO2 reduction with water oxidation through molecular devices to mimic natural photosynthesis is also discussed.

Conjugated microporous polymers (CMPs) have recently been investigated as an alternative approach to light-to-chemical energy conversion. In a previous paper, we reported an easy, safe, and low-cos...

Here, the synthesis of periodic mesoporous organosilicas (PMOs) containing large amounts of ruthenium(II) (Ru) tris(bipyridine) complexes within the pore walls as a solid photosensitizer is reported. The PMOs containing Ru complexes (Ru-PMOs) are synthesized from highly purified Ru complex precursors with three attached alkylsilatrane groups in the presence of a nonionic surfactant (triblock copolymer) using polyacrylic acid as a promoter. The Ru-PMOs show strong absorption in the visible light region up to 600 nm due to a metal–ligand charge transfer band, and redox behaviour at ≈0.8 V versus Ag/AgNO3 due to one-electron oxidation, that are very similar to those of homogeneous Ru(dmb)3(PF6)2 (dmb = 4,4′-dimethyl-2,2′-bipyridine) solution, despite the fact that the Ru complexes are embedded in the pore walls at high density. Ru-PMOs loaded with platinum metal or iridium oxide provide efficient photocatalysis for hydrogen evolution or water oxidation, respectively, under irradiation with visible light up to 600 nm in the presence of sacrificial agents. These results indicate that Ru-PMO is a versatile solid photosensitizer for the construction of various heterogeneous photocatalytic systems simply by placing catalytic materials in the stable mesochannels.

An easy, safe and low-cost synthesis of conjugated microporous polymers and related carbonized microporous materials is highly desirable for practical use. Here, we report the synthesis of 9,9′-spirobifluorene-based conjugated microporous organic polymers (COPs) starting from unsubstituted spirobifluorene using an inexpensive FeCl3 mediator. Three kinds of COPs, synthesized by FeCl3-mediated oxidative polymerization, Friedel–Crafts polymerization, and competitive oxidative/Friedel–Crafts polymerization of the spirobifluorene precursor, showed large surface areas (940–1980 m2 g−1) and high micropore volumes (0.5–0.9 cm3 g−1). The COPs synthesized by competitive oxidative/Friedel–Crafts polymerization were found to show a high gas uptake ability which is almost comparable to that of the previously reported spirobifluorene-based microporous organic polymers prepared by Yamamoto polymerization using an expensive Ni catalyst. The COPs were easily transformed into microporous carbons by direct carbonization without the addition of any activating agents. The carbonization process enhanced the gas uptake ability of the COPs at low pressure (1 atm), although the surface area and micropore volume were almost unchanged or slightly decreased. The FeCl3-mediated competitive oxidative/Friedel–Crafts polymerization of non-functionalized aromatics would be a useful synthetic approach for an easy, safe and low-cost synthesis of conjugated microporous polymers.

A highly photoluminescent (PL) porous covalent triazine-based framework (PCTF-8) is synthesized from tetra(4-cyanophenyl)ethylene by using trifluoromethanesulfonic acid as the catalyst at room temperature. Due to triazine units in the framework, the PCTF-8 exhibits excellent thermal stability (>400 °C). The Brunauer–Emmett–Teller (BET) specific surface area of PCTF-8 is 625 m2 g−1 which is lower than the one obtained from the synthesis under Lewis acid conditions (ZnCl2). At 1 bar and 273 K, the PCTF-8 adsorbs a significant amount of CO2 (56 cm3 g−1) and CH4 (17 cm3 g−1) which is highly comparable to nanoporous 1,3,5-triazine frameworks (NOP-1-6, 29–56 cm3 g−1). This nitrogen rich framework exhibits good ideal selectivity (61 : 1 (85% N2 : 15% CO2) at 273 K, 1 bar). Thus, it can be used as a promising candidate for potential applications in post-combustion CO2 capture and sequestration technologies. In addition, photoluminescence properties as well as the sensing behaviour towards nitroaromatics have been demonstrated. The fluorescence emission intensity of PCTF-8 is quenched by ca. 71% in the presence of 2,4,6-trinitrophenol (TNP). From time-resolved studies, a static quenching behaviour was found. This high photoluminescence property is used for hydrogen evolving organic photocatalysis from water in the presence of a sacrificial electron donor and a cocatalyst.

Periodic mesoporous organosilicas (PMOs), synthesized via surfactant-directed self-assembly of a polysilylated organic precursor (R[Si(OR')

Integration of functional molecular parts into nanoporous materials in a state that allows intermolecular charge or energy transfer is one of the key approaches to the development of photofunctional and electroactive materials. Herein, we report charge separation in a functionalized framework of a periodic mesoporous organosilica (PMO) self-assembled by hydrogen bonds. Electroactive π-conjugated organic species with different electron-donating and electron-accepting properties were selectively fixed onto the external surface of a nanoparticulate PMO, within the pore wall, and onto the surface of the internal mesopore. UV irradiation of the modified PMO resulted in photoinduced electron transfer and charge separation from the external surface to the pore wall and from the pore wall to the surface of the internal mesopores. These results suggest the high potential of multifunctionalized PMOs in the construction of photocatalytic reaction fields.

Periodic mesoporous organosilicas (PMOs), synthesized via surfactant-directed self-assembly of a polysilylated organic precursor (R[Si(OR')3]n; n≥2, R: organic group), are promising candidates such as catalysts and adsorbents, and for use in optical and electrical devices, owing to their high surface area, well-defined nanoporous structure, and highly functional organosilica framework. Their framework functionality can be widely tuned by selecting appropriate organic groups and controlling their arrangement. This chapter describes the synthesis and structure of PMOs with simple organic groups such as ethane and benzene, and the unique properties and optical applications of functional PMOs. Special light-harvesting properties and their exploitation in photocatalysis, highly emissive PMOs and their application to color-tunable transparent films, hole-transporting PMOs and their use in organic solar cells, and PMOs containing chelating ligands and their use as solid supports for heterogeneous metal complex catalysis are described.

This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO)