Search

Metal-organic frameworks (MOFs) stand as one of the most promising materials for the development of advanced technologies owing to their unique combination of properties. The conventional synthesis of MOFs involves a direct reaction of the organic linkers and metal salts; however, their postsynthetic modification is a sophisticated route to produce new materials or to confer novel properties that cannot be attained through the traditional methods. This work describes the postsynthetic MOF-to-MOF transformation of a nonluminescent MOF (Zn-based Oxford University-1 material [Zn-BDC, where BDC = 1,4-benzene dicarboxylate] (OX-1)) into a highly luminescent framework (Ag-based Oxford University-2 material [Ag-BDC] (OX-2)) by a simple immersion of the former in a silver salt solution. The conversion mechanism exploits the uncoordinated oxygen atoms of terephthalate linkers found in OX-1, instead of the unsaturated metal sites commonly employed, making the reaction much faster. The materials derived from the OX-1 to OX-2 transformation are highly luminescent and exhibit a selective response to acetone, turning them into a promising candidate for manufacturing fluorometric sensors for the diagnosis and monitoring of diabetes mellitus. Our methodology can be extended to other metals such as lead (Pb). The fabrication of a polymer mixed-matrix membrane containing OX-1 is used as a proof-of-concept for capturing Pb ions (as pollutants) from water. This research instigates the exploration of alternative methodologies to confer MOFs with special aptitudes for photochemical sensing or for environmental applications such as water purification.

Advances in energy‐efficient lighting and display technologies demand innovative materials with tailored broad‐spectrum emission properties. Hybrid aggregation‐induced emission metal‐organic frameworks (AIE‐MOFs) offer a promising avenue, combining unique characteristics of organic and inorganic components to yield enhanced luminescence efficiency and robust material stability. The study introduces a spectrum of D (donor)‐A (acceptor) type AIE‐active ligands into MOFs, enabling tunable emission across the visible spectrum, thus underscoring the versatility of these hybridized MOF materials. The emission properties of AIE‐MOFs are further harnessed by integrating them into polymer matrices, resulting in high‐performance electrospun fibers with tunable emission. A significant achievement involves the fabrication of Janus‐type white light‐emitting AIE‐MOF fiber composites via side‐by‐side electrospinning, accomplishing a high quantum yield of 58%, which doubled the performance of homogeneous fibers. Complementing the experimental findings, micro‐Raman and nano‐Fourier transform infrared spectroscopy are employed as local spectroscopic probes, affording a deeper understanding of the material properties and the mechanisms contributing to enhance light emission. In the understanding, this study presents an unconventional implementation of hybrid AIE‐MOFs in Janus‐type structures for white light emission. It significantly improves the efficiency of white light sources in optoelectronics, charting a promising direction for future research in the emergent AIE‐MOF field. [ABSTRACT FROM AUTHOR]

Luminescent metal‐organic frameworks (LMOFs) are promising materials for nanophotonic applications due to their tuneable structure and programmability. Yet, the 3D nature of LMOFs creates challenges for stability, optical transparency, and device integration. Metal‐organic nanosheets (MONs) potentially overcome these limitations by combining the benefits of metal‐organic frameworks (MOFs) with an atomically thin morphology of large planar dimensions. Herein, the bottom‐up synthesis of few‐layer thin ZIF‐7‐III MONs via facile low‐energy salt‐templating is reported. Employing guest@MOF design, the fluorophores Rhodamine B and Fluorescein are intercalated into ZIF‐7 nanosheets (Z7‐NS) to form light emissive systems exhibiting intense and highly photostable fluorescence. Aggregation and Förster resonance energy transfer, enabled by the MON framework, are revealed as the mechanisms behind fluorescence. By varying guest concentration, these mechanisms provide predictable quantified control over emission chromaticity of a dual‐guest Z7‐NS material and the definition of an "emission chromaticity fingerprint" – a unique subset of the visible spectrum that a material can emit by fluorescence. [ABSTRACT FROM AUTHOR]

This review addresses the latest advancements in the integration of aggregation‐induced emission (AIE) materials with polymer electrospinning, to accomplish fine‐scale electrospun fibers with tunable photophysical and photochemical properties. Micro‐ and nanoscale fibers augmented with AIE dyes (termed AIEgens) are bespoke composite systems that can overcome the limitation posed by aggregation‐caused quenching, a critical deficiency of conventional luminescent materials. This review comprises three parts. First, the reader is exposed to the basic concepts of AIE and the fundamental mechanisms underpinning the restriction of intermolecular motions. This is followed by an introduction to electrospinning techniques pertinent to AIE‐based fibers, and the core parameters for controlling fiber architecture and resultant properties. Second, exemplars are drawn from latest research to demonstrate how electrospun nanofibers and porous films incorporating modified AIEgens (especially tetraphenylethylene and triphenylamine derivatives) can yield enhanced photostability, photothermal properties, photoefficiency (quantum yield), and improved device sensitivity. Advanced applications are drawn from several promising sectors, encompassing optoelectronics, drug delivery and biology, chemosensors and mechanochromic sensors, and innovative photothermal devices, among others. Finally, the outstanding challenges together with potential opportunities in the nascent field of electrospun AIE‐active fibers are presented, for stimulating frontier research and explorations in this exciting field. [ABSTRACT FROM AUTHOR]

A series of host-activated Tb3+ and Eu3+-co-doped CaNb2O6 (CNO) phosphors with tunable luminescence were synthesized via high-temperature solid-state method with the purpose of developing single-component phosphors for white light-emitting diode (LED) devices. Benefiting from blue broadband emission of CNO and multiple energy transfer of NbO43− → Tb3+ → Eu3+, white light-emitting CNO:Tb3+, Eu3+ phosphors were achieved by reasonably adjusting the doping content of Tb3+ and Eu3+ ions. Two typical white light-emitting phosphors, CNO:0.015Tb3+, 0.02Eu3+ with color coordinate (0.33, 0.33) and CNO:0.10Tb3+, 0.05Eu3+ with color coordinate (0.40, 0.39), could maintain 63% and 73% of the initial integral intensity at 150 °C and had good color stability. Subsequently, the representative CNO:0.015Tb3+, 0.02Eu3+ phosphors were successfully applied to a 275 nm ultraviolet chip to fabricate a white LED device with a low correlated color temperature of 3464 K and a high color rendering index of 86.0. The above results indicate that synthesized single-component white light-emitting CNO:Tb3+, Eu3+ phosphors have good application prospects in the field of white LED. Moreover, this strategy of using self-activated host and multiple energy transfer also provides guidance for the design of novel white light-emitting phosphors. [ABSTRACT FROM AUTHOR]

A series of rhodamine B (RhB) encapsulated zeolitic imidazolate framework-8 (RhB@ZIF-8) composite nanomaterials with different concentrations of guest loadings have been synthesized and characterized in order to investigate their applicability to solid-state white-light-emitting diodes (WLEDs). The nanoconfinement of the rhodamine B dye (guest) in the sodalite cages of ZIF-8 (host) is supported by fluorescence spectroscopic and photodynamic lifetime data. The quantum yield (QY) of the luminescent RhB@ZIF-8 material approaches unity when the guest loading is controlled at a low level: 1 RhB guest per ~7250 cages. We show that the hybrid (luminescent guest) LG@MOF material, obtained by mechanically mixing a suitably high-QY RhB@ZIF-8 red emitter with a green-emitting fluorescein@ZIF-8 "phosphor" with a comparably high QY, could yield a stable, intensity tunable, near-white light emission under specific test conditions described. Our results demonstrate a novel LG@MOF composite system exhibiting a good combination of photophysical properties and photostability, for potential applications in WLEDs, photoswitches, bioimaging and fluorescent sensors. [ABSTRACT FROM AUTHOR]

Researches on tunable luminescence and temperature sensitivity of phosphors have become an increasingly popular trend. This paper reports a series of Ca 2 YZr 2 Al 3 O 12 (CYZA):Bi3+, Sm3+ phosphors prepared by solid-state reaction. The phase purity, energy transfer, luminescent properties and temperature sensing performance of the phosphors have been carefully studied. CYZA:Bi3+, Sm3+ phosphors excited by ultraviolet light show tunable color emission, and the color shifts from dark blue to pink due to Bi3+→Sm3+ energy transfer. The related luminescent mechanism of phosphors is also explained. In addition, according to the different thermal sensitivity of Bi3+ and Sm3+, the temperature sensitivity of the phosphors is studied by fluorescence intensity ratio model. The maximum values of absolute sensitivity and relative sensitivity reach up to 0.099% K−1 at 423 K and 0.356% K−1 at 473 K, respectively. These findings indicate that CYZA:Bi3+, Sm3+ phosphors are potential candidates for tunable luminescence and temperature sensing. • The color-tunable property can be obtained in CYZA:Bi3+, Sm3+ phosphors. • Energy transfer from Bi3+ to Sm3+ ions. • Different thermal attenuation behaviors of Bi3+ and Sm3+ ions. • Temperature sensing performance is investigated by FIR model. [ABSTRACT FROM AUTHOR]