The use of collective variables and enhanced sampling in the simulations of existing and emerging microporous materials

Microporous materials, including zeolites, metal-organic frameworks, and cage compounds, offer diverse functionalities due to their unique dynamics and guest confinement properties. These materials play a significant role in separation, catalysis, and sensing, but their complexity hinders exploration using traditional atomistic simulations. This review explores collective variables (CVs) paired with enhanced sampling as a powerful approach to enable efficient investigation of key features in microporous materials. We highlight successful applications of CVs in studying adsorption, diffusion, phase transitions, and mechanical properties, demonstrating their crucial role in guiding material design and optimisation. The future of CVs lies in integration with techniques like machine learning, allowing for enhanced efficiency and accuracy. By tailoring CVs to specific materials and developing multi-scale approaches we can further unlock the intricacies of these fascinating materials. Simulations are a cornerstone in unravelling the complexities of microporous materials and are crucial for our future understanding.

Red-Emitting Latex Nanoparticles by Stepwise Entrapment of β-Diketonate Europium Complexes

The core-shell structure of poly(St-co-MAA) nanoparticles containing β-diketonate Eu³⁺ complexes were synthesized by a step-wise process. The β-diketonate Eu³⁺ complexes of Eu (TFTB)₂(MAA)P(Oct)₃ [europium (III); 4,4,4-Trifluoro-1-(2-thienyl)-1,3-butanedione = TFTB; trioctylphosphine = (P(Oct)₃); methacrylic acid = MAA] were incorporated to poly(St-co-MAA). The poly(St-co-MAA) has highly monodispersed with a size of 300 nm, and surface charges of the poly(St-co-MAA) are near to neutral. The narrow particle size distribution was due to the constant ionic strength of the polymerization medium. The activated carboxylic acid of poly(St-co-MAA) further chelated with europium complex and polymerize between acrylic groups of poly(St-co-MAA) and Eu(TFTB)₂(MAA)P(Oct)₃. The E_m spectra of europium complexes consist of multiple bands of E_m at 585, 597, 612 and 650 nm, which are assigned to ⁵D₀→⁷F_{J (J = 0-3)} transitions of Eu³⁺, respectively. The maximum E_m peak is at 621 nm, which indicates a strong red E_m characteristic associated with the electric dipole ⁵D₀→⁷F₂ transition of Eu³⁺ complexes. The cell-specific fluorescence of Eu(TFTB)₂(MAA)P(Oct)₃@poly(St-co-MAA) indicated endocytosis of Eu(TFTB)₂(MAA)P(Oct)₃@poly(St-co-MAA). There are fewer early apoptotic, late apoptotic and necrotic cells in each sample compared with live cells, regardless of the culture period. Eu(TFTB)₂(MAA)P(Oct)₃@poly(St-co-MAA) synthesized in this work can be excited in the full UV range with a maximum E_m at 619 nm. Moreover, these particles can substitute red luminescent organic dyes for intracellular trafficking and cellular imaging agents.

Ultrahighly Sensitive Sandwich-Type Electrochemical Immunosensor for Selective Detection of Tumor Biomarkers

Herein, a novel sandwich-type immunosensor was designed using Pt nanoparticle-decorated SnS₂ nanoplates (Pt@SnS₂) as a matrix and N,B-doped Eu MOF (N,B-Eu MOF) nanospheres as a signal amplifier. In Pt@SnS₂, Pt nanoparticles (NPs) enhance the surface electron transport capability and electrochemiluminescence (ECL) performance of SnS₂ nanoplates. The dual "antenna" effect of 5-boronoisophthalic acid (5-bop) and 5-nitroisophthalic acid (5-nop) enables the N,B-Eu MOFs to show very good ECL performance at the cathode. In the presence of the target carcinoembryonic antigen (CEA), the sandwich-type immunosensor provides specific immune responses, and the ECL signal of the immunosensor is greatly amplified by the signal probe N,B-Eu MOFs. In view of the above, the immunosensor was successfully applied for highly sensitive and selective detection of CEA with a detection limit of 0.06 pg·mL^-1. This sensor exhibits high sensitivity and specificity, excellent stability, good reproducibility, and good practicability in real human serum.

Recyclable Luminescent Sensor for Detecting Creatinine Based on a Lanthanide-Organic Framework

Creatinine is an important clinical marker for human health, but detecting it by a luminescent sensor based on metal-organic frameworks is rarely investigated. In this work, we synthesized a new lanthanide-organic framework {[Tb(L)(CH₃COO)(H₂O)]·0.5DMF}_n (1) (H₂L = 3,5-bis(4'-carboxy-phenyl)1,2,4-triazole) with good solvent and acid/alkaline stabilities. Experimental results indicate that 1 can be used in the detection of creatinine in an aqueous solution with a wide linear detection range from 3.27 to 371 μM, and the detection limit can reach 1.7 × 10^-6 M based on the 3σ method, which is less than the pathogenic concentration in a real environment. In addition, this luminescent sensor can also monitor the concentration changes of creatinine in diluted serum solutions and can be recycled at least five times, suggesting that it has a potential application for clinical monitoring.

Asymmetric Lumino-Transformer: Circularly Polarized Luminescence of Chiral Eu(III) Coordination Polymer with Phase-Transition Behavior

A chiral Eu(III) coordination polymer with phase-transition behavior, [Eu(+tfc)₃(m-dpeb)]_n, (+tfc: (+)-3-trifluoroacetylcamphorato, m-dpeb: 1,3-bis(diphenylphosphorylethynyl)benzene) was reported for understanding the effect of polymer chain arrangement (orientation effect) on the circularly polarized luminescence (CPL) in a solid system. The phase-transition behavior of the transformable Eu(III) coordination polymer was characterized using differential scanning calorimetry and powder X-ray diffraction. The Eu(III) coordination polymer exhibited phase transition at approximately 180 °C. The magnitude of the CPL intensity was drastically changed because of the phase transition, without coordination geometrical change around the Eu(III) ion. In this study, the orientation effect of a chiral Eu(III) coordination polymer on the CPL properties in crystalline solid is demonstrated.

Novel 2D isomorphic lanthanide complexes based on a bifunctional 5-(pyridin-3-yloxy)isophthalic acid: synthesis, structure, fluorescence and magnetic properties

The Tb(iii)-complex can be used as a multifunctional luminescent sensor presenting visual quenching responses towards acetone, Fe3+ and CrO42− in aqueous solution with high sensitivity and low detection limits.

The postsynthetic renaissance of luminescent lanthanide ions on crystalline porous organic framework materials

A series of crystalline porous organic framework materials (CPOFs), such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen bonded organic frameworks (HOFs) have received extensive attentions due to...

Self-Healing Material with Reversible Luminescence Switch Behavior

Luminescent materials with dynamic responsiveness to external stimuli have attracted extensive attention for the development of advanced sensors and smart materials; however, self-healing capability is also of great importance for functional soft materials. An acid/base vapor reversibly triggered luminescence switch with self-healing ability is achieved by incorporating dynamic lanthanide metal-ligand (Ln-L) coordination into the soft polydimethylsiloxane polymer network. The emission color of the resultant luminescent material could be modulated by altering either the Eu³⁺/Tb³⁺ molar ratio or the excitation wavelength. The luminescence "On-Off" reversible switch is realized via direct alternating exposure to acid and base vapor, realizing reversible information encryption and decryption. The dynamic Ln-L cross-link as well as the hydrogen bond in the luminescent material endow it with excellent self-healing capability, high toughness, and stretchability. We believe this acid/base vapor-triggered self-healing switching strategy provides new insights for expanding the application range of luminescent materials.

Thermo-responsive light-emitting metal complexes and related materials

This review discusses the fundamentals and design strategies for the development of thermo-responsive metal–ligand coordination materials and the applications of these materials in temperature sensing, bioimaging, information security, etc.

First Ln-MOF as a trifunctional luminescent probe for the efficient sensing of aspartic acid, Fe3+ and DMSO

The first Ln-MOF (Tb-MOF) as a trifunctional luminescent probe for the efficient sensing of aspartic acid, Fe³⁺ and DMSO was demonstrated.

Highly chemically and thermally stable lanthanide coordination polymers for luminescent probes and white light emitting diodes

A series of isomorphic of highly chemically and thermally stable lanthanide coordination polymers exhibit luminescent probe and warm white-light emission.

Syntheses of three new isostructural lanthanide coordination polymers with tunable emission colours through bimetallic doping, and their luminescence sensing properties

Tuning the emissive color changes of lanthanide (Ln) complexes is an important and appealing project for promoting the applications of Ln-complexes. A solvothermal reaction of 4-cyano-3-methylbenzoic acid (HL) and Ln(NO3)3·6H2O affords three isostructural Ln-complexes [Eu(L)3(H2O)2]n (1-Ln) (Ln = Eu, Gd and Tb) with one-dimensional chain structures. 1-Eu and 1-Tb show bright red and green emissions with absolute quantum yields of 3.06% and 11.96%, respectively, and the energy transfer was analyzed in detail through combined calculations. Interestingly, a series of heterometallic doped 1-TbxEu1-x coordination polymers were also obtained by mixing different ratios of Eu3+ and Tb3+ ions, which possess continuous luminescent color changes from green to yellow, orange and red. In addition, 1-Eu exhibits high quenching efficiency and low detection limit (∼10-4 M) for the simultaneous sensing of MnO4-, CrO42- and Cr2O72- ions in water.

Metallopolymers for advanced sustainable applications

Since the development of metallopolymers, there has been tremendous interest in the applications of this type of materials. The interest in these materials stems from their potential use in industry as catalysts, biomedical agents in healthcare, energy storage and production as well as climate change mitigation. The past two decades have clearly shown exponential growth in the development of many new classes of metallopolymers that address these issues. Today, metallopolymers are considered to be at the forefront for discovering new and sustainable heterogeneous catalysts, therapeutics for drug-resistant diseases, energy storage and photovoltaics, molecular barometers and thermometers, as well as carbon dioxide sequesters. The focus of this review is to highlight the advances in design of metallopolymers with specific sustainable applications.

Structural Manipulation of Triboluminescent Lanthanide Coordination Polymers by Side-Group Alteration

Novel Eu(III) coordination polymers with furan-based bridging ligands [Eu(hfa)₃(Cy)] _n and [Eu(hfa)₃(Tol)] _n (hfa: hexafluoroacetylacetonato, Cy: 2,5-bis(dicyclohexylphosphoryl)furan), Tol: 2,5-bis(di- p-tolylphosphoryl)furan) are reported. The rigidity of assembly steric structures was controlled by intermolecular interactions through the side groups in bridging ligands. They exhibited one of the best performances (thermal stability above 320 °C and external photoluminescence quantum yields of up to 71%) among reported lanthanide(III) compounds. The triboluminescence activity was demonstrated to be dependent on the mechanical stability of the coordination polymers, which was proportional to the number of hydrogen atoms in the side groups. The second example of a large TL/PL spectral difference in [Tb,Eu(hfa)₃(Tol)] _n also revealed discrete photophysical processes under the conditions of grinding and UV irradiation.

The effect of ligand symmetry on the ratiometric luminescence characteristics of lanthanides

This work demonstrated that the ligand symmetry of europium(iii) complexes controls the ratiometric luminescence characteristics of lanthanides. Nona-coordinated europium(iii) complexes having unsymmetrical β-diketonate ligands (Cs) exhibit distinctive ratiometric spectral variations in the extremely narrow f-f transition bands over the temperature range from 253 to 323 K. In contrast, no such ratiometric change can be observed in a series of nona-coordinated europium(iii) complexes containing symmetrical β-diketonate ligands (C2v). The remarkable difference depending on the ligand symmetry (Csvs. C2v) suggests that the coordination rearrangement of β-diketonate in the complex causes ratiometric spectral variations in extremely narrow f-f transition bands, where two europium(iii) complex isomers exist in the solution equilibrium. A self-calibration method using dual iso-emissive points is reported, where self-calibration using the two emission intensities at the iso-emissive points reduces the coefficient of variation in luminescence thermometry.

Europium-based infinite coordination polymer nanospheres as an effective fluorescence probe for phosphate sensing

Uniform europium-based infinite coordination polymer nanospheres have been successfully fabricated as an effective fluorescence probe for phosphate sensing.

Luminescent rare-earth-based MOFs as optical sensors

This perspective article highlights the basics and applications of luminescence-based sensing of hazardous chemicals, pH, and temperature using rare-earth-based metal–organic frameworks.

Hyper-stable organo-Eu(III) luminophore under high temperature for photo-industrial application

Novel organo-Eu(III) luminophores, Eu(hfa)x(CPO)y and Eu(hfa)x(TCPO)y (hfa: hexafluoroacetylacetonate, CPO: 4-carboxyphenyl diphenyl phosphine oxide, TCPO: 4,4',4″-tricarboxyphenyl phosphine oxide), were synthesized by the complexation of Eu(III) ions with hfa moieties and CPO or TCPO ligands. The thermal and luminescent stabilities of the luminophores are extremely high. The decomposition temperature of Eu(hfa)x(CPO)y and Eu(hfa)x(TCPO)y were determined as 200 and 450 °C, respectively. The luminescence of Eu(hfa)x(TCPO)y under UV light irradiation was observed even at a high temperature, 400 °C. The luminescent properties of Eu(hfa)x(CPO)y and Eu(hfa)x(TCPO)y were estimated from emission spectra, quantum yields and lifetime measurements. The energy transfer efficiency from hfa moieties to Eu(III) ions in Eu(hfa)x(TCPO)y was 59%. The photosensitized luminescence of hyper-stable Eu(hfa)x(TCPO)y at 400 °C is demonstrated for future photonic applications.

Syntheses, crystal structures and properties of metal–organic rotaxane frameworks with cucurbit[6]uril

Five new cucurbit[6]uril-based MORFs are hydrothermally synthesized by the mixed ligand strategy and their fluorescence properties have been investigated.

Preparation, characterization, and properties of PMMA-doped polymer film materials: a study on the effect of terbium ions on luminescence and lifetime enhancement

Poly(methylmethacrylate) (PMMA) doped with Tb-based imidazole derivative coordination polymer {[Tb(3)(L)(μ(3)-OH)(7)]·H(2)O}(n) (1) (L = N,N'-bis(acetoxy)biimidazole) was synthesized and its photophysical properties were studied. The L'(L' = N,N'-bis(ethylacetate)biimidazole) ligand was synthesized by an N-alkylation reaction process followed by ester hydrolysis to produce ligand L. Polymer 1 and ligand L' have been characterized by (1)H NMR and IR spectroscopy, elemental analysis, PXRD and X-ray single-crystal diffraction. Coordination polymer 1 is the first observation of a CdCl(2) structure constructed with hydroxy groups and decorated by ligand L in lanthanide N-heterocyclic coordination polymers. In the 2D layered structure of 1, each Tb3 metal center is connected with three Tb1 and three Tb2 metal centers by seven hydroxyl groups in different directions, resulting in a six-membered ring. After doping, not only the luminescence intensity and lifetime enhanced, but also their thermal stability was increased in comparison with 1. When 1 was doped into poly(methylmethacrylate) (1@PMMA), polymer film materials were formed with the PMMA polymer matrix (w/w = 2.5%-12.5%) acting as a co-sensitizer for Tb(3+) ions. The luminescence intensity of the Tb(3+) emission at 544 nm increases when the content of Tb(3+) was 10%. The lifetime of 1@PMMA (914.88 μs) is more than four times longer than that of 1 (196.24 μs). All τ values for the doped polymer systems are higher than coordination polymer 1, indicating that radiative processes are operative in all the doped polymer films. This is because PMMA coupling with the O-H oscillators from {[Tb(3)(L)(μ(3)-OH)(7)]·H(2)O}(n) can suppress multiphonon relaxation. According to the variable-temperature luminescence (VT-luminescence) investigation, 1@PMMA was confirmed to be a stable green luminescent polymer film material.

Metal-organic frameworks for artificial photosynthesis and photocatalysis

Solar energy is an alternative, sustainable energy source for mankind. Finding a convenient way to convert sunlight energy into chemical energy is a key step towards realizing large-scale solar energy utilization. Owing to their structural regularity and synthetic tunability, metal-organic frameworks (MOFs) provide an interesting platform to hierarchically organize light-harvesting antennae and catalytic centers to achieve solar energy conversion. Such photo-driven catalytic processes not only play a critical role in the solar to chemical energy conversion scheme, but also provide a novel methodology for the synthesis of fine chemicals. In this review, we summarize the fundamental principles of energy transfer and photocatalysis and provide an overview of the latest progress in energy transfer, light-harvesting, photocatalytic proton and CO2 reduction, and water oxidation using MOFs. The applications of MOFs in organic photocatalysis and degradation of model organic pollutants are also discussed.