Series of Stable Anionic Lanthanide Metal-Organic Frameworks as a Platform for Pollutant Separation and Efficient Nanoparticle Catalysis

Eu(III) functionalized ZnMOF based efficient dual-emission sensor integrated with self-calibrating logic gate for intelligent detection of epinephrine

The rapid detection of epinephrine (EPI) in serum holds immense importance in the early disease diagnosis and regular monitoring. On the basis of the coordination post-synthetic modification (PSM) strategy, a Eu3+ functionalized ZnMOF (Eu3+@ZnMOF) was fabricated by anchoring the Eu3+ ions within the microchannels of ZnMOF as secondary luminescent centers. Benefiting from two independent luminescent centers, the prepared Eu3+@ZnMOF shows great potential as a multi-signal self-calibrating luminescent sensor in visually and efficiently detecting serum EPI levels, with high reliability, fast response time, excellentrecycleability, and low detection limits of 17.8 ng/mL. Additionally, an intelligent sensing system was designed in accurately and reliably detecting serum EPI levels, based on the designed self-calibrating logic gates. Furthermore, the possible sensing mechanisms were elucidated through theoretical calculations as well as spectral overlaps. This work provides an effective and promising strategy for developing MOFs-based self-calibrating intelligent sensing platforms to detect bioactive molecules in bodily fluids.

A mechanochemically synthesized Schiff-base engineered 2D mixed-linker MOF for CO2 capture and cationic dye removal

Developing synthetic strategies for smart materials for the adsorption and separation of toxic chemicals is of great importance. Metal-organic frameworks (MOFs) have been proven to be outstanding adsorbent materials that possess excellent pollutant removal performances in wastewater treatment, including dye recycling. In this work, a neutral Cd(II) based 2D framework with a dual ligand strategy involving -OH functionalized 5-hydroxyisophthalic acid (5-OH-H2IPA) and the amide decorated Schiff base ligand (E)-N'-(pyridin-4-ylmethylene)isonicotinohydrazide (L) has been synthesized by different synthetic routes and characterized by various analytical methods. Thus, crystals of {[Cd(5-OH-IPA)(L)]·CH3OH}n synthesized via diffusion (ADES-7D) and the phase pure bulk product synthesized by conventional reflux (ADES-7C) and the mechanochemical grinding method (ADES-7M) have been established using PXRD data of the respective product showing identical simulated SXRD data to those of ADES-7D. The mechanochemically synthesized ADES-7M possesses a better surface area and CO2 adsorption capability compared to ADES-7C, which is also supported by electron microscopy and particle size measurements. Furthermore, ADES-7 can be used as an efficient adsorbent material for the reversible, selective adsorption (42-99%) and separation of the cationic dyes malachite green (MG), methyl violet (MV), methylene blue (MB), and rhodamine B (RhB) from the mixture of cationic/anionic dyes (methyl orange (MO) and bromocresol green (BCG)) in the aqueous phase. Specifically, ADES-7M possesses better dye capture capability compared to ADES-7C, even in the case of the bigger dye RhB with adsorption differences of 2.38 to 1.01 mg g-1, respectively. The dye adsorption kinetics follows pseudo-second-order kinetics, and the dye adsorption isotherm fits well with the Langmuir/Freundlich adsorption isotherm models. The probable mechanism of adsorption involving the supramolecular interaction between the host MOF and the guest dye has also been proposed.

Two-Dimensional Lanthanide Metal-Organic Frameworks as a Platform for Sensing Pollutant and Nitrophenols Reduction

The discharge of harmful and toxic pollutants in water is destroying the ecosystem balance and human being health at an alarming rate. Therefore, the detection and removal of water pollutants by using stable and efficient materials are significant but challenging. Herein, three novel lanthanide metal-organic frameworks (Ln-MOFs), [La(L)(DMF)2(H2O)2]·H2O (LCUH-104), [Nd(L)(DMF)2(H2O)2]·H2O (LCUH-105), and [Pr(L)(DMF)2(H2O)2]·H2O (LCUH-106) [H3L = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid (H3TZI)] were solvothermally constructed and structurally characterized. In the three Ln-MOFs, dinuclear metallic clusters {Ln2} were connected by deprotonated tetrazol-containing dicarboxylate TZI3- to obtain a 2D layered framework with a point symbol of {42·84}·{46}. Their excellent chemical and thermal stabilities were beneficial to carry out fluorescence sensing and achieve the catalytic nitrophenols (NPs) reduction. Especially, the incorporation of the nitrogen-rich tetrazole ring into their 2D layered frameworks enables the fabrication of Pd nanocatalysts (Pd NPs@LCUH-104/105/106) and have dramatically enhanced catalytic activity by using the unique metal-support interactions between three Ln-MOFs and the encapsulating palladium nanoparticles (Pd NPs). Specifically, the reduction of NPs (2-NP, 3-NP, and 4-NP) in aqueous solution by Pd NPs@LCUH-104 exhibits exceptional conversion efficiency, remarkable rate constants (k), and outstanding cycling stability. The catalytic rate of Pd NPs@LCUH-104 for 4-NP is nearly 8.5 times more than that of Pd/C (wt 5%) and its turnover frequency value is 0.051 s-1, which indicate its excellent catalytic activity. Meanwhile, LCUH-105, as a multifunctional fluorescence sensor, exhibited excellent fluorescence detection of norfloxacin (NFX) (turn on) and Cr2O72- (turn off) with high selectivity and sensitivity at a low concentration, and the corresponding fluorescence enhancement/quenching mechanism has also been systematically investigated through various detection means and theoretical calculations.

In Situ Implantation of Bi2S3 Nanorods into Porous Quasi-Bi-MOF Architectures: Enabling Synergistic Dissociation of Borohydride for an Efficient and Fast Catalytic Reduction of 4-Nitrophenol

Catalytic hydrogenation reduction based on sodium borohydride (NaBH₄) has gained attention as an appealing "one-stone-two-birds" approach for the simultaneous elimination of nitroaromatic pollutants and the production of high-value aminoaromatics under mild conditions. However, the slow kinetics of NaBH₄ dissociation on the surface of catalysts restrict the catalytic hydrogenation reduction efficiency. Herein, we report an intelligent localized sulfidation strategy for an in situ implantation of Bi₂S₃ nanorods within quasi-Bi-MOF architectures (Bi₂S₃@quasi-Bi-MOF) by fine-tuning the pyrolysis temperature. In this novel Bi₂S₃@quasi-Bi-MOF, the porous quasi-Bi-MOF enables efficient adsorption of BH₄^- and 4-nitrophenol (4-NP), while Bi₂S₃ facilitates the BH₄^- dissociation to form H_ads* species adsorbed on the catalyst surface. Benefiting from the synergistic structure, Bi₂S₃@quasi-Bi-MOF exhibits excellent performance for the catalytic reduction of 4-NP, delivering a high turnover frequency (TOF) of 1.67 × 10^-4 mmol mg^-1 min^-1 and an extremely high normalized rate constant (k_nor) of 435298 s^-1 g^-1. The kinetic analysis and electrochemical tests indicate that this catalytic hydrogenation reduction follows the Langmuir-Hinshelwood mechanism. This study enriches the synthetic strategy of MOF-based derivatives and offers a new catalytic platform for hydrogenation reduction reactions.

Series of TM-OFs as a Platform for Efficient Catalysis and Multifunctional Luminescence Sensing

Three novel porous transition-metal-organic frameworks (TM-OFs), formulated as [Co₃(DCPN)₂(μ₂-OH₂)₄(H₂O)₄](DMF)₂ (1), [Cd₃(DCPN)₂(μ₂-OH₂)₄(H₂O)₄](DMF)₂ (2), and [CdK(DCPN)(DMA)] (3), have been successfully prepared via solvothermal conditions based on a 5-(3',6'-dicarboxylic phenyl) nicotinic carboxylic acid (H₃DCPN) ligand. 1 and 2 both have the same porous 3D network structure with the point symbol of {4¹⁰·6¹⁴·8⁴}·{4⁵·6}₂ based on trinuclear ({Co₃} or {Cd₃}) clusters, indicating a one-dimensional porous channel, and possess excellent water and thermal stability; 3 also displays a porous 3D network structure with a 4-connected sra topology based on the heteronuclear metal cluster {CdK}. Complex 1 can be used to load Pd nanoparticles (Pd NPs) via a wetness impregnation strategy to obtain Pd@1. The reduction of nitrophenols (2-NP, 3-NP, 4-NP) by Pd@1 in aqueous solution shows outstanding conversion, excellent rate constants (k), and remarkable cycling stability due to the synergistic effect of complex 1 and Pd NPs. Luminescence sensing tests confirmed that 2 is a reliable multifunctional chemical sensor with high selectivity and sensitivity for low concentrations of Fe³⁺, Cr₂O₇^2-, CPFX, and NFX. Specifically, 2 shows a fluorescence enhancement behavior toward fluoroquinolone antibiotics (CPFX and NFX), which has not been reported previously in the literature. Moreover, the rational mechanism of fluorescence sensing was also systematically investigated by various detection means and theoretical calculations.

Substituent Dependence on Series of Cationic Gyroidal MOFs in utc-c Topology with High CO2 Affinity and Ultrahigh Anionic Dye Adsorption Capacity

A substituent decorating strategy for modification of the functional cavity is of great importance in the design of metal-organic frameworks (MOFs). Herein, three new isostructural cationic MOFs, [Cu₃(Xpip)₂]·NO₃·nH₂O (Xpip stands for X-substituted phenylimidazophenanthroline, where X = adm (SCNU-2), f (SCNU-3), and none for SCNU-4), have been successfully synthesized and shown gyroidal utc-c topology and large pore sizes which can be adjusted by different substituents (-N(CH₃)₂, -F, and -H). Interestingly, the differences of the substituents (sizes and proton donor/acceptor) show essential effects on the adsorption abilities of carbon dioxide and dyes, where SCNU-4 exhibits the highest CO₂ affinity and the biggest adsorption capacity for anionic dyes Fluorescein Sodium, and SCNU-3 adsorbs the largest amount (1503.6 mg/g) of Acid Fuchsin to date for the reported porous materials. The detailed studies in adsorption kinetics, adsorption isotherms, and theoretical calculation of the binding energies between the structures and dye molecules confirm that the electric properties of the frameworks (cationic) and substituents directed to the pore surface are two important factors dramatically affecting the selective dye adsorption.