Porous Hybrid Materials Research Articles

Fast Dynamic Synthesis of MIL-68(In) Thin Films in High Optical Quality for Optical Cavity Sensing.

Fabrication of metal-organic framework (MOF) thin films rigidly anchored on suitable substrates is a crucial prerequisite for the integration of these porous hybrid materials into electronic and optical devices. Thus, far, the structural variety for MOF thin films available through layer-by-layer deposition was limited, as the preparation of those surface-anchored metal-organic frameworks (SURMOFs) has several requirements: mild conditions, low temperatures, day-long reaction times, and nonaggressive solvents. We herein present a fast method for the preparation of the MIL SURMOF on Au-surfaces under rather harsh conditions: Using a dynamic layer-by-layer synthesis for MIL-68(In), thin films of adjustable thickness between 50 and 2000 nm could be deposited within only 60 min. The MIL-68(In) thin film growth was monitored in situ using a quartz crystal microbalance. In-plane X-ray diffraction revealed oriented MIL-68(In) growth with the pore-channels of this interesting MOF aligned parallel to the support. Scanning electron microscopy data demonstrated an extraordinarily low roughness of the MIL-68(In) thin films. Mechanical properties and lateral homogeneity of the layer were probed through nanoindentation. These thin films showed extremely high optical quality. By applying a poly(methyl methacrylate) layer and further depositing an Au-mirror to the top, a MOF optical cavity was fabricated that can be used as a Fabry-Perot interferometer. The MIL-68(In)-based cavity showed a series of sharp resonances in the ultraviolet-visible regime. Changes in the refractive index of MIL-68(In) caused by exposure to volatile compounds led to pronounced position shifts of the resonances. Thus, these cavities are well suited to be used as optical read-out sensors.

Metal-Organic Frameworks (MOFs) as Solid State Hydrogen Storage System: A Critical Review

Metal organic frameworks (MOFs) are a class of hybrid porous materials which consists inorganic and organic linkers bounded to metal ions. The important properties of MOFs such as greater surface area, synthetic versatility, variable pore size, long range order and inherent structure makes MOFs very interesting in the field of hydrogen storage. In this manuscript we are reporting a detailed review on metal organic frameworks with the help of available previous reported literature. This review summarizes MOFs structure aspect, synthesis, nomenclature, progress of MOFs, gas storage applications, energy consumption, hydrogen storage targets, tabulation of MOFs for hydrogen storage and limitations of synthesized MOFs system related technologies, present challenges and importance of MOFs as hydrogen storage system.

Concentration and LBL cycle evolution to the Cu-BTC metal organic framework: Optimization as functional layer to the solar cell devices

Metal-organic frameworks are rational self-assembly of metal-ions and organic-linkers, and are class of hybrid porous materials those endowed with unique physiochemical properties. To seek cost effective renewable energy resources, solar cell technology has potential to cater futuristic energy need of society, where MOFs may play an important role to develop cost effective and eco-friendly devices. Therefore, in this work, properties of Copper-based MOFs are investigated in aspect to functional layer applications to solar cell devices where synthesis of Cu3(BTC)2 MOFs is accomplished by establishing coordination between Copper (II) ions and 1,3,5 benzene tricarboxylic acid (BTC) linker using solvothermal method. Developed Cu3(BTC)2 MOFs are subjected to various characterization tools where, structural analysis revealed dominance of (222) reflection and successful formation of Copper-based frameworks. Thermogravimetric analysis indicated first and second weight losses corresponding to temperature ranges of 114–130 °C and 360–375 °C, respectively. FTIR analysis exposed presence of symmetric and asymmetric modes of carboxylic groups and CH bending mode. Surface morphological analysis revealed to the formation of pyramidal coordination geometry of Copper-based frameworks whereas compositional analysis confirmed successful synthesis of Cu3(BTC)2 frameworks. The solar cell devices having architecture as Glass/FTO/TiO2/Cu-BTC/CuSCN/Ag are fabricated with 5, 10, and 15 LBL cycles of Cu-BTC MOFs. The device with 10 LBL cycles exhibited better performance vis-à-vis the others. The attained results signify that synthesized bulk Cu-BTC MOF material and device fabricated with 10 LBL cycles draw attention to further undertake materials evolution for development of high performance solar cell devices.

Post-Synthetic Surface Modification of Metal-Organic Frameworks and Their Potential Applications.

Metal-organic frameworks (MOFs) are porous hybrid materials with countless potential applications. Most of these rely on their porous structure, tunable composition, and the possibility of incorporating and expanding their functions. Although functionalization of the inner surface of MOF crystals has received considerable attention in recent years, methods to functionalize selectively the outer crystal surface of MOFs are developed to a lesser extent, despite their importance. This article summarizes different types of post-synthetic modifications and possible applications of modified materials such as: catalysis, adsorption, drug delivery, mixed matrix membranes, and stabilization of porous liquids.

A Time of Change

A Time of Change

Sulfonic Acid-Grafted Hybrid Porous Polymer Based on Double-Decker Silsesquioxane as Highly Efficient Acidic Heterogeneous Catalysts for the Alcoholysis of Styrene Oxide.

β-Alkoxyalcohols generated from epoxide ring-opening reactions are significant due to their enormous value as pharmaceutical intermediates and fine chemicals. Using a phenyl-substituted double-decker-type silsesquioxane as the precursor, a hybrid porous material (PCS-DDSQ) was synthesized through a Scholl coupling reaction with an AlCl3 catalyst. Then, novel excellent Brønsted acid-derived silsesquioxane solid catalysts (PCS-DDSQ-SO3H-x) were successfully obtained through an electrophilic aromatic substitution reaction of chlorosulfonic acid on phenyl rings of PCS-DDSQ, fully characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, powder X-ray diffraction, temperature-programmed desorption, water contact angle, Brunauer-Emmett-Teller model, thermogravimetric analysis, and solid-state 13C and 29Si nuclear magnetic resonance techniques. The catalytic behavior of the PCS-DDSQ-SO3H-x with different SO3H loadings for the methanolysis of styrene oxide was compared and evaluated. The presence of SO3H groups endows them with excellent catalytic abilities, achieving the highest values from PCS-DDSQ-SO3H-1 (the acid site of its catalyst is 1.84 mmol/g) as 99% conversion and 100% selectivity for the methanolysis of styrene oxide in 30 min, which shows superior catalytic properties of low dosage and high efficiency. Furthermore, the PCS-DDSQ-SO3H-1 catalyst can maintain high activity and selectivity after three cycles. This study provides a feasible method for the preparation of Brønsted solid acid catalysts with different acid loadings by introducing the sulfonic group into PCS-DDSQ.

On the role of graphene oxide in bifunctional Ni/MOF/rGO composites in electrochemical nitrate detection and oxygen evolution reaction

Bi-functional metal organic frameworks as promising porous framework hybrid materials for electrochemical nitrate sensing and oxygen evolution reaction.

Abnormal magnetic phenomenon at low temperature in Zn doped <inline-formula><tex-math id="M1">\begin{document}$ \left[{(\mathbf{C}\mathbf{H}}_{3}{)}_{2}\mathbf{N}{\mathbf{H}}_{2}\right]{\mathbf{C}\mathbf{o}}_{\mathit{x}}{\mathbf{Z}\mathbf{n}}_{1-\mathit{x}}{\left[\mathbf{H}\mathbf{C}\mathbf{O}\mathbf{O}\right]}_{3} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20221761_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20221761_M1.png"/></alternatives></inline-formula> frameworks

Metal-organic framework (MOF) is a new type of inorganic-organic hybrid porous material composed of organic ligands bridging metal ions, and it has the characteristics of tunable functions, good stability and porosity. In this study, Zn doped Co-based metal organic frame works single-crystal samples<inline-formula><tex-math id="M2">\begin{document}$\left[{(\rm{C}\rm{H}}_{3}{)}_{2}\rm{N}{\rm{H}}_{2}\right]{\rm{C}\rm{o}}_{1-x}{\rm{Z}\rm{n}}_{x} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20221761_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20221761_M2.png"/></alternatives></inline-formula><inline-formula><tex-math id="M2-1">\begin{document}$ {\left[\rm{H}\rm{C}\rm{O}\rm{O}\right]}_{3}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20221761_M2-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="3-20221761_M2-1.png"/></alternatives></inline-formula>are synthesized by the solvothermal method with normal ratio <i>x</i> = 0, 0.1, 0.2, 0.3, 0.4, 0.5. Single crystal diffraction, scanning electron microscope and energy dispersive X-ray spectroscopy results show that Zn ions are uniformly doped into Co-based MOFs crystals. The field cooling curves show that antiferromagnetic phase transition temperature of Co-based MOFs decreases from 15 K for pure Co-MOF <i>x</i> = 0 to 12.8 K for <i>x</i> = 0.2. Abnormal large magnetic hysteresis is obtained for Zn doped crystals with large coercive field 3600 Oe (<i>x</i> = 0.3) compared with 450 Oe coercive field for pure Co-MOF (<i>x</i> = 0), and the hysteresis area of Zinc-doped sample is more than 3 times that of pure cobalt sample. On the other hand, we find a series of steps on the hysteresis loop of DMCo<sub>0.9</sub>Zn<sub>0.1</sub>F sample, which gradually disappears with the increase of temperature, similar to the quantum tunneling phenomenon of a single molecule magnet. Previous studies have shown that the long range magnetic interaction and the magnetic single-ion behavior competition coexist in these systems. It is believed that the doping of non-magnetic zinc ions weakens the long-range interaction between Co ions and makes Co ions show the step effect caused by quantum tunneling at low temperature.

Microporous Polymelamine Framework Functionalized with Re(I) Tricarbonyl Complexes for CO2 Absorption and Reduction.

A mixture of polymeric complexes based on the reaction between Re(CO)5Cl and the porous polymeric network coming from the coupling of melamine and benzene-1,3,5-tricarboxaldehyde was obtained and characterized by FTIR, NMR, SEM, XPS, ICP, XRD, and cyclic voltammetry (CV). The formed rhenium-based porous hybrid material reveals a noticeable capability of CO2 absorption. The gas absorption amount measured at 295 K was close to 44 cm3/g at 1 atm. An interesting catalytic activity for CO2 reduction reaction (CO2RR) is observed, resulting in a turn over-number (TON) close to 6.3 under 80 min of test at -1.8 V vs. Ag/AgCl in a TBAPF6 0.1 M ACN solution. A possible use as filler in membranes or columns can be envisaged.

Mn-1,4-BDC MOF based a COF for ultrafast and simultaneous removal of cationic dyes

We utilized the benefits of two promising classes of porous hybrid materials via the combination of Mn-1,4-benzenedicarboxylate (Mn-1,4-BDC) metal–organic framework (MOF) and imine-linked melamine and terephthaldehyde covalent organic framework (COF) using the solvothermal method. The resultant hybrid material (Mn-1,4-BDC/COF) was analyzed by variant methodology inclusive of FT-IR, XRD, FE-SEM, STA, and BET. The synthesized Mn-1,4-BDC/COF was used as a robust adsorbent to quick simultaneous removal of auramine O (AO) and rhodamine B (RB) via hydrogen bonding, electrostatic communication, π-π piling and Lewis acid-base association from aqueous media. The effective operational variables which include pH, Mn-1,4-BDC/COF mass, sonication time, and initial dyes concentration were cross-examined and optimized. The optimum conditions were found to be at pH = 8, 0.016 g Mn-1,4-BDC/COF dosage, and 8 min sonication time. Mn-1,4-BDC/COF adsorbent exhibited the adsorption capacity of 21.53 and 25.13 mg/g for AO and RB, respectively. The isotherm and kinetic studies reveal a suitable fit for the Langmuir isotherm and the pseudo-second-order kinetics models, respectively.

Tailoring of 2D MoS2 microspheres on 3D low-cost DE for the efficient removal of hazardous cationic dyes

The primary challenge involved in the water treatment field is to treat/clean the contaminated waste dye solutions before it releases into the environment. Industrial contaminant such as dyes are released into water streams, rendering the water unfit for further use. Treatment of such dye contaminants is still a challenging tasks that has evolved as one of the leading issues in environmental remediation. Some of the significant limitations in dye adsorption include time-consuming, synthetic routes, expensive adsorbents, more contact time, less adsorption performances and use of more adsorbents. To address such problems, herein in this work, 2D MoS2 molybdenum disulfide)-3D DE (diatomaceous earth) hybrid materials were synthesized by a facile and efficient hydrothermal route. The prepared innovative combination of 2D & 3D porous hybrid materials demonstrated to be efficient adsorbents for the efficient removal of malachite green (MG) dye from aqueous solution with superior 97 % removal efficiency within 5 mins and with an extended 60 mins of contact time possible to achieve 99.9 % of removal efficiency. Furthermore, the maximum adsorption capacity for DE was only 0.78 mg/g and developed 2D MoS2-3D DE exhibited an outstanding 110 mg/g for MB dye which is a significant improvement when compared to pristine DE. On the other hand, the 2D MoS2-3D DE was explored as a membrane-based filter for the removal of other important cationic pollutant methylene blue (MB) dye which showed 100 % rejection for varied MB volumes from 50 to 200 mL with average flux rate of 2200 L.m−2.h−1. Additionally, the 2D-3D hybrid adsorbents substantiated with better recyclability with up to 5 cycle performances which could be an excellent candidate for the removal of industrially important cationic dyes in the future.

Responsive shape recognition of styrene over ethylbenzene with excellent selectivity and capacity in a hybrid porous material

The efficient separation of styrene and ethylbenzene remains a challenge in the petrochemical industry due to their similar physical properties and kinetic molecular sizes. Here we for the first time report the responsive shape recognition of styrene over ethylbenzene according to the conformational differences caused by different substituent groups, using a hybrid porous material ZU-61 with adaptive nano-traps in response to styrene molecules specifically. Single-crystal X-ray diffraction studies reveal that the rotation of pyridine ring in ZU-61 triggered by guest molecules opens a styrene nano-trap with proper pore shape and high-density of electrostatic anion sites for styrene adsorption, but limits the entrance of oversized ethylbenzene. The styrene uptake capacity of ZU-61 reaches a record high of 5.2 mmol/g and dynamic breakthrough experiments also confirm the excellent separation selectivity of styrene/ethylbenzene (10.8 in vapor phase).

Application of photo-responsive metal-organic framework in cancer therapy and bioimaging

Metal-organic frameworks (MOFs) are a class of hybrid porous crystalline materials that are assembled with metal ions/clusters and organic linkers. The fungibility of organic ligands and metal centers endow MOFs that are easy to design and synthesize. Based on their unique structure, multifarious MOFs with diverse functionalities have recently been widely applied in various research areas. Particularly striking is the application of photo-responsive MOFs in biological sensing and imaging. Notably, the photoelectronic properties make photo-responsive MOFs an ideal platform for cancer phototherapy. Moreover, ultrahigh porosities and tunable pore sizes allow MOFs to load anticancer drugs, further enhancing the antitumor efficiency. In this review, the categories and developing strategies of MOFs are briefly introduced. The application fields of MOFs in bioimaging, such as up-conversion fluorescence imaging, single/two-photon fluorescence bioimaging, magnetic resonance imaging, etc., are summarized. The working mechanism of MOFs in photo-responsive, photothermal therapy (PTT), and photodynamic therapy (PDT) are expounded. Examples of using MOFs for cancer treatment, including PTT, PDT, chemotherapy, and radiotherapy, are also demonstrated. Lastly, current limitations, challenges, and future perspectives for bioimaging and cancer treatment of MOFs are discussed. We believe that the versatile MOF will bring the dawn to the next generation of cancer treatment.

MOF-derived metal sulfides for electrochemical energy applications

• Progresses on MOFs-derived metal sulfides in energy storage/conversion systems were summarized. • Challenges and opportunities of MOFs-derived metal sulfides were discussed. • Optimization strategies for improving electrochemical performance were concluded. As a new crystalline porous organic-inorganic hybrid materials, metal organic frameworks (MOFs) have been proved to be the ideal precursors for the preparation of metal sulfides, with higher catalytic potential and excellent catalytic activity in electrocatalysis as well as enhanced reversible capacity, superior rate, and cycle performance in electric energy storage. In this review, the recent progress (synthesis methods, compositions, structures, and reaction mechanisms) of MOF-derived metal sulfides for batteries (lithium-ion batteries, lithium-sulfur batteries, sodium-ion batteries, potassium ion batteries and so on), supercapacitors, and electrocatalysis have been summarized. At last, the challenges and opportunities faced by the future development of this field are put forward, hoping to provide some enlightenment for the synthesis of MOF-derived metal sulfides, so as to create more efficient and lasting electrochemical energy storage and conversion systems.

Water adsorption characterization of bivalent metal doped HKUST-1

Bivalent metal doping onto the framework affects the water sorption characteristics of HKUST-1. • HKUST-1 was synthesized according to a hydrothermal synthesis process. • Two alkaline metal ions (Ca 2+ and Mg 2+ ) and two transitional metal ions (Zn 2+ and Co 2+ ) were doped in situ. • The MM-HKUST-1 MOFs were isostructural with the pristine MOF. • High surface area, large pore volume, and good thermal stability was observed. • Water sorption characteristics were affected by bivalent metal cation doping. • Co-HKUST-1 presented the maximum water loading capabilities with the highest SCE. Metal-organic frameworks (MOFs) are inorganic–organic hybrid porous crystalline materials featured by exceptionally high surface area, tunable porosity, and controllable chemical structures, making them efficient candidates for gas adsorption. HKUST-1 is a promising MOF constructed from the coordination bonding of copper paddle-wheel metal nodes and 1,3,5-benzenetricarboxylates. In this study, HKUST-1 was synthesized according to a hydrothermal synthesis procedure, and two alkaline metal ions (Ca 2+ and Mg 2+ ) and two transitional metal ions (Co 2+ and Zn 2+ ) were individually doped in situ in the framework of HKUST-1. The synthesized pristine HKUST-1 and the metal-doped MM-HKUST-1 were then characterized experimentally. MM-HKUST-1 samples were isostructural with the pristine MOF, and larger surface area and increased pore volume were observed due to metal doping. The effect of the presence of different metals on the water sorption capacity was investigated by volumetric water sorption analysis. The incorporation of metal ions Co 2+ and Mg 2+ enhanced the affinity towards water vapor, whereas the equilibrium uptake capacity of the other two metal-doped samples was comparable with the parent one. The increased water uptake capacity eventually increased the SCE of the Co-HKUST-1 sample for providing cooling of 15 °C with heat source temperatures of 50 °C and 60 °C.

Framework for discovering porous materials: Structural hybridization and Bayesian optimization of conditional generative adversarial network

Although deep-learning-based materials discovery has attracted considerable research attention, the application of deep learning has been limited to discovery of materials within single material types such that the discovered materials are similar to existing ones. Thus, we developed an alternative approach for discovering porous materials. A materials discovery design space was configured using several key porous materials and a conditional generative adversarial network (CGAN), which structurally hybridizes them. Hybridization was controlled using a vector design variable input as a condition to the CGAN, and each design variable component represented a key porous material intensity, which was defined as a conceptual quantity for expressing materialness. Furthermore, by varying the vector latent variable input to the CGAN, any number of similar hybrid porous materials could be generated using the same design variable. The multiobjective Bayesian optimizer efficiently discovered hybrid porous materials constituting Pareto solutions in the objective function space of the material properties, which were mapped from the design space by the CGAN structural hybridization and computational fluid dynamics property evaluation. Tradeoff properties such as the pressure drop and filtration efficiency were multiobjectively optimized for key porous materials exhibiting random, packed-sphere, and sponge structures. By flexibly adopting their structural parameters depending on the required pressure drop and filtration efficiency, the discovered optimized hybrid porous materials outperformed the key porous ones. The results demonstrated the effectiveness of the proposed framework for discovering porous materials.

GeFSIX‐1‐Cu based semi‐interpenetrating network mixed matrix membranes for efficient CO2 separation

AbstractIn order to increase CO2 separation efficiency, semi‐interpenetrating network mixed matrix membranes (SIPN‐MMMs) were loaded with GeFSIX‐1‐Cu (Cu(4,4′‐bipyridine)2(GeF6)) and poly ethylene glycol dimethyl ether (PEGDME). Two long‐chain polymers poly ethylene glycol diacrylate (PEGDA) and poly ethylene glycol methyl ether acrylate (PEGMEA) jointly constituted a crosslinked PEO backbone, and CO2‐philic short‐chain polymer PEGDME and anion‐pillared hybrid porous materials GeFSIX‐1‐Cu were embedded into the backbone to introduce strong CO2 adsorption sites and provide extra pore channels. Increasing GeFSIX‐1‐Cu loading in SIPN‐MMMs initially improved CO2 permeability and CO2/N2, CO2/CH4, and CO2/H2 selectivity, because the porous structure of GeFSIX‐1‐Cu provides additional pore channels for gas transport. In addition, the strong binding affinity between GeF62− and CO2 leads to improved membrane selectivity. When GeFSIX‐1‐Cu loading increased above 3 wt%, both CO2 permeability and CO2/N2, CO2/CH4, and CO2/H2 selectivity decreased, due to agglomeration of excess GeFSIX‐1‐Cu loading in SIPN‐MMMs. The highest CO2 permeability of 786 Barrer and CO2/N2 ideal selectivity of 43 (at GeFSIX‐1‐Cu loading of 3 wt%) were 36% and 38% higher than those of pure SIPN membrane, respectively, resolving the trade‐off between permeability and selectivity, and surpassing the Robeson upper bound (2008).

Facile Electrodeposition of NiCo2O4 Nanosheets on Porous Carbonized Wood for Wood-Derived Asymmetric Supercapacitors.

Multichannel-porous carbon derived from wood can serve as a conductive substrate for fast charge transfer and ion diffusion, supporting the high-theory capacitance of pseudocapacitive materials. Herein, NiCo2O4 nanosheets, which are hierarchically porous, anchored on the surface of carbonized wood via electrodeposition for free-binder high-performance supercapacitor electrode materials, were proposed. Benefiting from the effectively alleviated NiCo2O4 nanosheets accumulation and sufficient active surface area for redox reaction, a N-doped wood-derived porous carbon-NiCo2O4 nanosheet hybrid material (NCNS–NCW) electrode exhibited a specific electric capacity of 1730 F g−1 at 1 A g−1 in 1 mol L−1 KOH and splendid electrochemical firmness with 80% capacitance retention after cycles. Furthermore, an all-wood-based asymmetric supercapacitor based on NCNS–NCW//NCW was assembled and a high energy density of 56.1 Wh kg−1 at a watt density of 349 W kg−1 was achieved. Due to the great electrochemical performance of NCNS–NCW, we expect it to be used as an electrode material with great promise for energy storage equipment.

Europium-cadmium organic framework with zwitterionic ligand exhibiting tunable luminescence, CO2 adsorption and dye degradation

Porous lanthanide-transition heterometallic metal-organic frameworks (MOFs) as a subclass of porous hybrid materials have attracted considerable attention as a new advance in the research on MOFs. However, rationally designing and constructing heterometallic MOFs with desirable properties remains a challenging task. In this work, involving the heterometallic cooperative crystallization method, a novel europium-cadmium MOF based on a zwitterionic carboxylate ligand, [EuCd(pbbp)2(SO4)2Cl2(H2O)3] (1), (H2pbbp·2Cl ​= ​1,1'-(1,4-phenylene-bis(methylene))-bis(3-carboxy pyridinium) dichloride), has been solvothermally synthesized. Complex 1 was characterized by single-crystal X-ray diffraction, elemental analysis, infrared spectroscopy, and thermogravimetric analysis. The structure of complex 1 consists of Eu–Cd heterometallic chains with one-dimensional channels. Complex 1 shows interesting excitation-dependent luminescence at room temperature. The gas adsorption studies show that complex 1 exhibits highly selective adsorption of CO2 over N2 and H2 under ambient conditions, which may be caused by the stronger interaction of CO2 with the positively charged pyridinium functional groups. In addition, the photocatalytic activity studies indicate that complex 1 shows good activity in rhodamine B dye degradation.

Effect of nickel ion concentration on structural, optical and electrical properties towards Ni–H3BTC-MOF formation for nonlinear saturable absorption phenomenon

Metal-organic frameworks (MOFs) are a class of crystalline hybrid porous materials that have drawn considerable research interest owing to their tunable characteristics and wide range of applications. In this study, we investigated the effect of the nickel ion concentration on the structural, optical, and electrical properties of Ni–H3BTC-MOF for the potential nonlinear saturable absorbance phenomenon. Structural analysis was performed using Fourier transform infrared spectroscopy, X-ray diffraction and Brunauer–Emmett–Teller analysis, whereas diffuse reflectance UV–Vis–NIR spectroscopy was used to characterize the optical properties. The AC transport properties of the as-prepared Ni–H3BTC-MOF were investigated using electrical impedance spectroscopy. It was found that the porosity increased with an increasing concentration of nickel ions. In contrast, the real permittivity and loss tangent decreased. The highest modulation depth obtained was 4.48% for the sample with a nickel ion concentration of 2 mmol. This performance has been attributed to the low loss tangent (0.06–0.26), low real permittivity (11.3–23.9) F/m, median porosity (7.08 nm) and layered flower-shaped morphology of the material, all of which are desirable for the nonlinear saturable absorbance phenomenon.