Metal–organic frameworks (MOFs) display a wide range of luminescent behaviors resulting from the multifaceted nature of their structure. In this critical review we discuss the origins of MOF luminosity, which include the linker, the coordinated metal ions, antenna effects, excimer and exciplex formation, and guest molecules. The literature describing these effects is comprehensively surveyed, including a categorization of each report according to the type of luminescence observed. Finally, we discuss potential applications of luminescent MOFs. This review will be of interest to researchers and synthetic chemists attempting to design luminescent MOFs, and those engaged in the extension of MOFs to applications such as chemical, biological, and radiation detection, medical imaging, and electro-optical devices (141 references).

Luminescent Metal–Organic Frameworks

Lanthanide-based luminescent hybrid materials.

Interpretation of europium(III) spectra

Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can then be treated by conventional biological methods. The efficacy of AOPs depends on the generation of reactive free radicals, the most important of which is the hydroxyl radical (·OH). The authors summarize the formation reactions of ·OH and the mechanisms of pollutants degradation. They cover six types of advanced oxidation processes, including radiation, photolysis and photocatalysis, sonolysis, electrochemical oxidation technologies, Fenton-based reactions, and ozone-based processes. Controversial issues in pollutants degradation mechanism were discussed. They review t...

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application

We have synthesized the ternary organic/inorganic/polymeric terbium hybrid material (ACAC-Si)-Tb-PVP [ACAC = acetylacetone; PVP = poly(4-vinylpyridine)]. Firstly, the ACAC was modified through the hydrogen transfer addition reaction with a cross-linking reagent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) to obtain a functional molecular bridge ACAC-Si which subsequently coordinated with Tb3+ and thus formed the inorganic Si-O-Si networks with TEOS (tetraethoxysilane) through hydrolysis and polycondensation process, and PVP acted as organic polymeric chains was synthesized using 4-vinylpyridine as the monomer after coordination with Tb(III) in the presence of BPO (Benzoyl Peroxide). For comparison, the binary hybrid material Tb-(ACAC-Si) was also prepared. The properties of the two hybrid materials were characterized in detail. The results reveal that the terbium complex was embedded into the organic polymer matrix by covalent bond with uniform microstructure. Furthermore, the distinction of the excitation spectrum between the binary and ternary hybrid materials suggests that the introduction of the polymeric organic chain component changed the microenvironment around the coordination sphere of the terbium. The emission spectrum exhibit the strong characteristic fluorescence of Tb3+, which accounts for the efficient intro-molecular energy transfer taken place in the two hybrid materials.

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A new luminescent molecular based terbium hybrid material containing both organic polymeric chains and inorganic silica networks

Two novel luminescent temperature-sensitive poly(N-isopropylacrylamide) hydrogels fabricated with rare earth (Eu, Tb) picolinic acid complexes were in-situ synthesized within the interpenetration networks. Fluorescence spectra indicate the two functional gels exhibit red for Eu3+ species and green emissions for Tb3+ ones, respectively, whose luminescence intensities are changed due to temperature increasing from 5 to 30°C until totally quenched at lower critical solution temperature (33°C). In addition, the decreasing luminescence behavior obeys the simple linear equations. The releasing experiment substantiates that there may be complexation between O⩵C–NH⩵ moieties of P-NIPAA and Eu3+ ions for the prolonged released time.

Luminescent behavior of two novel thermo-sensitive poly(N-isopropylacrylamide) hydrogels incorporated with rare earth complexes.

Photoluminescent hybrid alumina and titania gels linked to rare earth complexes and polymer units through coordination bonds

Through the hydrogen transfer nucleophilic addition reaction between the hydroxyl groups of the glycol, the diglycol or the polyglycol and the isocyanate groups of 3-(triethoxysilyl)-propyl isocyanate (TEPIC), the hybrid precursor G–Si, DG–Si and PG–Si were obtained. And then G–Si, DG–Si or PG–Si has coordinated to the rare earth ions with the carbonyl groups to form the three kinds of hybrid materials through hydrolysis and copolycondensation with the tetraethoxysilane (TEOS) via sol–gel process. The data in NMR, FT-IR and ultraviolet absorption spectra indicate that the effective precursors have been obtained successfully. Moreover, seen from the fluorescent excitation and emission spectra, TG plots and electronic microscopy diagraphs, respectively, the obtained materials have the excellent fluorescent intensities, outstanding thermal stabilities and regular and homogenous trunk stripes microstructures. Ulteriorly, the X-ray diffraction patterns were obtained under the room temperature to describe the structure of the materials.

Molecular construction and photophysics of luminescent covalently bonded hybrids by grafting the lanthanide ions into the silicon–oxygen networks and carbon chains

Bing Yan

Papers

A new luminescent molecular based terbium hybrid material containing both organic polymeric chains and inorganic silica networks

Luminescent behavior of two novel thermo-sensitive poly(N-isopropylacrylamide) hydrogels incorporated with rare earth complexes.

Photoluminescent hybrid alumina and titania gels linked to rare earth complexes and polymer units through coordination bonds

Molecular construction and photophysics of luminescent covalently bonded hybrids by grafting the lanthanide ions into the silicon–oxygen networks and carbon chains

Sol–gel composition of multicomponent hybrid precursors to long afterglow of CaxSr1 − xAl2O4: Eu2+ phosphors