A highly stable terbium(III) metal-organic framework MOF-76(Tb) for hydrogen storage and humidity sensing

An Electron Beam Irradiation Postsynthetic Lanthanide-Based Metal-Organic Framework for Extraction of U(VI)

The development of highly efficient uranium adsorbents is pivotal for the sustainable advancement of nuclear energy. In this study, we present an innovative electron beam (EB) irradiation-assisted postsynthetic modification (PSM) strategy to engineer defects within a lanthanide-based metal-organic framework, MOF-76, significantly enhancing its U(VI) adsorption capacity. Compared to pristine MOF-76, the EB-modified MOF-76 demonstrates a remarkable increase in uranium removal efficiency, achieving the highest removal rate at a cumulative radiation dose of 120 kGy─twice that of the pristine material. A comprehensive suite of characterizations, including powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), CO2 sorption, electron paramagnetic resonance (EPR), X-ray photoelectron spectroscopy (XPS), and fluorescence lifetime and quantum yield measurements, confirms that the EB irradiation induces a high concentration of defects in MOF-76-120 kGy, primarily manifested as ligand vacancies, while preserving the overall framework structure and stability. XPS analysis further reveals that the irradiation-induced defects introduce numerous binding sites containing -COOH and -OH groups, which exhibit a strong affinity for U(VI). Our findings not only propel the development of advanced uranium extraction technologies but also offer valuable insights into the interactions between radiation and matter in porous crystalline systems.

Efficient Color Conversion in Metal-Organic Frameworks Boosts Optical Wireless Communications beyond 1 GB/s Data Rate

Efficient color converters are essential for achieving high -3-dB bandwidths and net data rates in optical wireless communications (OWCs). Here, we emphasize the significance of lanthanide-based metal-organic frameworks (MOFs) combined with an effective energy transfer strategy for developing high-performance color converters in OWC systems. In this approach, we successfully reduced the photoluminescence (PL) lifetime from 1.3 ms of the MOF to 4.6 ns of the MOF-chromophore composite, achieved through an efficient energy transfer process in the cavity and surface of the MOFs. This significant reduction in PL lifetime led to a dramatic increase in the -3-dB bandwidth, rising from less than 0.1 to 65.7 MHz. Most importantly, a net data rate of 1.076 GB/s was achieved, marking the first successful demonstration of lanthanide-based MOFs as color converters that facilitate data transmission rates exceeding 1 GB/s. Notably, both the -3-dB bandwidth and net data rate surpass those of most reported organic and inorganic materials, underscoring the exceptional potential of lanthanide-based MOFs when combined with an efficient energy transfer strategy. We believe this combination paves the way for further innovations in high-speed OWC technologies.

The influence of HKUST-1 and MOF-76 hand grinding/mechanical activation on stability, particle size, textural properties and carbon dioxide sorption

In this study, we explore the mechanical treatment of two metal-organic frameworks (MOFs), HKUST-1 and MOF-76, applying various milling methods to assess their impact on stability, porosity, and CO2 adsorption capacity. The effects of different mechanical grinding techniques, such as high-energy ball milling and hand grinding, on these MOFs were compared. The impact of milling time, milling speed and ball size during high-energy ball milling was assessed via the Design of Experiments methodology, namely using a 33 Taguchi orthogonal array. The results highlight a marked improvement in CO2 adsorption capacity for HKUST-1 through hand milling, increasing from an initial 25.70 wt.% (5.84 mmol g-1) to 41.37 wt.% (9.40 mmol g-1), marking a significant 38% increase. In contrast, high-energy ball milling seems to worsen this property, diminishing the CO2 adsorption abilities of the materials. Notably, MOF-76 shows resistance to hand grinding, closely resembling the original sample's performance. Hand grinding also proved to be well reproducible. These findings clarify the complex effects of mechanical milling on MOF materials, emphasising the necessity of choosing the proper processing techniques to enhance their stability, texture, and performance in CO2 capture and storage applications.

Enhancement of the sensing performance and stability of a MOF based-molecularly imprinted polymer by utilizing dual-ligands and triethanolamine catalysis

In this work, a terbium MOF-based molecularly imprinted polymer (Tb-MOF@SiO₂@MIP) was prepared using two ligands as organic linkers and triethanolamine (TEA) as a catalyst to improve the sensing performance and stability of the fluorescence sensors. The obtained Tb-MOF@SiO₂@MIP was then characterized using a transmission electron microscope (TEM), energy dispersive spectroscopy (EDS) Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). The results revealed that Tb-MOF@SiO₂@MIP was successfully synthesized with a thin imprinted layer of 76 nm. The synthesized Tb-MOF@SiO₂@MIP maintained 96% of its original fluorescence intensity after 44 days in aqueous environments because of appropriate coordination models between the imidazole ligands as a nitrogen donor and Tb (Ⅲ). Furthermore, TGA analysis results indicated that an increase in the thermal stability of Tb-MOF@SiO₂@MIP was attributed to the thermal barrier from a MIP layer. The Tb-MOF@SiO₂@MIP sensor responded well to the addition of imidacloprid (IDP) in the range of 2.07-150 ng mL^-1 with a low detection limit of 0.67 ng mL^-1. In vegetable samples, the sensor can quickly detect IDP levels with the average recovery ranging from 85.10 to 99.85% and RSD values ranging from 0.59 to 5.82%. The UV-vis absorption spectrum and density functional theory analysis results revealed that the inner filter effect and dynamic quenching process both contributed to the sensing process of Tb-MOF@SiO₂@MIP.

Humidity Sensors Based on Metal-Organic Frameworks

Humidity sensors are important in industrial fields and human activities. Metal-organic frameworks (MOFs) and their derivatives are a class of promising humidity-sensing materials with the characteristics of a large specific surface area, high porosity, modifiable frameworks, and high stability. The drawbacks of MOFs, such as poor film formation, low electrical conductivity, and limited hydrophilicity, have been gradually overcome with the development of material science. Currently, it is moving towards a critical development stage of MOF-based humidity sensors from usability to ease of use, of which great challenges remain unsolved. In order to better understand the related challenges and point out the direction for the future development of MOF-based humidity sensors, we reviewed the development of such sensors based on related published work, focusing on six primary types (impedance, capacitive, resistive, fluorescent, quartz crystal microbalance (QCM), and others) and analyzed the sensing mechanism, material design, and sensing performance involved, and presented our thoughts on the possible future research directions.