Cadmium-organic Framework Research Articles

Fabrication of C and N co-doped CdS semiconductor photocatalysts derived from a novel Cd-MOF for enhancing photocatalytic performance

The narrow bandgap value and long lifetime of photo generated charges make CdS exhibit higher photocatalytic activity compared to other semiconductor catalysts. Given the excellent optoelectronic properties of CdS, a novel 2D cadmium-organic framework (Cd-MOF) was obtained by solvothermal method, which was served as a precursor template in this paper. C and N co-doped CdS-T (T = 600/800/1000) semiconductor materials were successfully prepared by chemical deposition method under different high temperatures. The as-prepared materials had been characterized in detail. Furthermore, the Cd-MOF and CdS-T were used to conduct the photocatalytic activity of organic dyes. Among them, CdS-800 showed excellent photocatalytic degradation effects on five organic dyes, especially on RB with the photocatalytic degradation efficiency of 98.87 %, which was significantly improved 6.5 times compared to Cd-MOF (58.23 %). Free radical capture experiments have shown that •O2− play a dominant role in the photocatalytic process. In addition, UV–vis diffuse reflection, photoluminescence (PL), photoelectrochemical (PEC) testing and density functional theory (DFT) calculations had shown that CdS-800 could effectively delay the recombination of photo generated charges, improve the rapid migration and separation of photo generated carriers, and enhance photocatalytic activity. This work provides new ideas for the preparation of efficient and recyclable CdS semiconductor photocatalytic materials.

A Pyridazine‐Based Cadmium(II) Organic Framework With pcu Topology as a Luminance Sensor to Nitrobenzene, Al(III), and Cu(II) Ion

ABSTRACTIn the field of water decontamination, the design of luminance sensor for sensitive detection of heavy metal ion toxic and nitroaromatic compounds are important and challenging. Herein, a new luminescent Cd(II) metal–organic framework (MOF), {[Cd2(H2O)3(4‐CPCA)2]·2H2O}n (SNUT‐27) (H2(4‐CPCA) = 1‐(4‐carboxyphenyl)‐4‐oxo‐1,4‐dihydropyridazine‐3‐carboxylic acid) was obtained by the reaction of flexible ligand H2(4‐CPCA) and Cd(II) ions, characterized by single crystal X‐ray diffraction, PXRD, FT‐IR, and TGA, the samples were further analyzed. The analysis of single crystal X‐ray diffraction showed that SNUT‐27 possesses a distinct three‐dimensional spatial arrangement and demonstrates impressive fluorescence properties. Particularly, SNUT‐27 showed a highly sensitive response to the nitro‐aromatic compounds nitrobenzene by fluorescence quenching, and in contrast, showed a fluorescence enhancement response to Al3+ and Cu2+. SNUT‐27 can be effortlessly recycled by simply rinsing with water post‐sensing experiments, showcasing its reusability. Additionally, potential detection mechanisms have been explored.

Selective Adsorption of Dyes and Fe3+ Sensing via Tb3+ Incorporation in an Anionic Cadmium-Organic Framework.

A three-dimensional (3D) anionic cadmium-organic framework, namely [(CH3)2NH2][Cd1.5(DMTDC)2] ⋅ 2DMA ⋅ 0.5H2O (Cd-MOF; DMA=N,N-dimethylacetamide), was successfully synthesized under solvothermal conditions by using a linear thienothiophene-containing dicarboxylate ligand, 3,4-dimethylthieno [2,3-b]-thiophene-2,5-dicar-boxylic acid (H2DMTDC). Single-crystal X-ray diffraction analysis reveals that Cd-MOF exhibits a 3D anionic framework with pcu α-Po topology, featuring rectangle and rhombus-shaped channels along b- and c- axis direction. Cd-MOF demonstrates selective adsorption of cationic dyes over anionic and neutral dyes. Additionally, Tb3+-loaded Cd-MOF serves as a fast-response fluorescence sensor for the sensitive detection of Fe3+ ions with a low limit of detection (8.90×10-7 M) through fluorescence quenching.

Fabrication of a Terbium-Functionalized Cadmium Organic Framework with Proper Energy Levels as a Ratiometric Probe of an Anthrax Biomarker.

Anthrax bacillus is a very dangerous zoonotic pathogen that seriously endangers public health. Rapid and accurate qualitative and quantitative detection of its biomarkers, 2,6-dipicolinic acid (DPA), is crucial for the prevention and treatment of this pathogenic bacterium. In this work, a novel Cd-based MOF (TTCA-Cd) has been synthesized from a polycarboxylate ligand, [1,1':2',1″-terphenyl]-4,4',4″,5'-tetracarboxylic acid (H4TTCA), and further doped with Tb(III), forming a dual-emission lanthanide-functionalized MOF hybrid (TTCA-Cd@Tb). TTCA-Cd@Tb can be developed as a high-performance ratiometric fluorescent sensor toward DPA with a very low detection limit of 7.14 nM and high selectivity in a wide detection range of 0-200 μM, demonstrating a big advancement and providing a new option for the detection of DPA.

Fabrication of a novel 3D cadmium−organic framework doped with europium as multifunctional fluorescence probes for enhancing detectability

A novel 3D cadmium−organic framework (Cd-MOF) was prepared based on ionothermal synthesis method and successfully doped with Eu3+ cations to obtain Eu@Cd-MOF by postsynthetic modification method. Cd-MOF has a strong and stable framework due to the balance of cations on the overall structure. Using characterization methods such as powder X-ray powder diffraction (PXRD), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetry analysis (TGA), these two materials have excellent solvent and chemical stability. More interestingly, both two materials can be used as multifunctional fluorescent probes to detect Fe3+, Co2+, Cr2O72−, MnO4−, and NB, and exhibit significant sensitivity, anti-interference, and recyclability. It is worth noting that compared to the original Cd-MOF, Eu@Cd-MOF enhanced excellent quenching effect on Fe3+, Co2+, Cr2O72−, MnO4−, and NB. Related to this, we conducted detailed research and discussion on possible fluorescence sensing mechanisms. This work extends propositions to the design and doped with europium of ionothermal synthesis MOFs, and explores their potential applications in the field of fluorescence sensing.

Series of Cadmium-Organic Frameworks Based on Mixed Flexible and Rigid Ligands: Single-Crystal-to-Single-Crystal Transformations, Sorption, and Luminescence Properties.

Here, we present a series of Cd(II) coordination polymers containing two types of ligands: sterically rigid terephthalate derivatives (bdc-NO22- and bdc-Br2-) and flexible bis(2-methylimidazolyl)propane (bmip). The combination of two types of ligands is used to obtain and characterize compounds by single crystal and powder X-ray diffraction, FT-IR, elemental analysis, and TGA. Guest exchange results in structural transformations. 2-fold interpenetrated 1·DMF and 2·DMF rapidly undergo to 4-fold interpenetrated 1·Et2O, 1·EtOH, and 1·H2O, or 2·Et2O, respectively. Also, changes in the coordinating numbers and length of the N,N'-donor bmip ligand were observed according to single crystal X-ray analysis. Activated guest-free compounds [Cd(bdc-NO2)(bmip)] (1) and [Cd(bdc-Br)(bmip)] (2) are shown to be porous with a BET surface area of 103 and 283 m2·g-1, respectively. Moreover, both compounds demonstrate gate-opening behavior of ethylene adsorption isotherms at low pressures (<1 bar) and highly selective adsorption of benzene over cyclohexane or lower alcohols. Also, both compounds demonstrate a strong dependence of the maximum of the photoluminescence emission on an excitation wavelength. As a result, the photoluminescence color changes from white to red and from blue to red through green and yellow for compounds 1 and 2, respectively, with excitation wavelength changing from 360 to 540 nm.

Three-Dimensional Cadmium–Organic Framework with Dual Functions of Oxygen Evolution in Water Splitting and Fenton-like Photocatalytic Removal of Organic Pollutants

Metal-organic frameworks (MOFs) have exhibited appreciable potential as catalytic agents in the field of material science. The research of new MOFs with dual functions in electrocatalysis and photocatalysis under ultraviolet (UV) irradiation is extremely pivotal for renewable energy applications. Hence, we synthesized a series of three-dimensional MOFs, namely, [Cd(bimb)2(HITA)2]n (Cd-MOF 1), {[Cd(bimb)6](NO3)2}n (Cd-MOF 2), and [Cd(bimb)4(ONO2)2]n (Cd-MOF 3) (bimb = 1,4-bis(imidazol-1-ylmethyl)benzene; H2ITA = 5-hydroxyisophthalic acid), with applicability in the oxygen evolution reaction process and Fenton-like photocatalysis. The obtained results show that Cd-MOF 1 exhibited the most remarkable catalytic performance, affording a current density of 10 mA cm-2 at a very low overpotential of 279 mV and the smallest Tafel slope of 85.13 mV dec-1. Meanwhile, these MOFs can generate hydroxyl radicals (•OH) under UV light irradiation with the existence of H2O2, enabling the rapid degradation of organic pollutants. This study provides a valuable direction for producing multifunctional and environmentally friendly catalysts.

Light-Assisted CO2 Cycloaddition over a Nanochannel Cadmium–Organic Framework Loaded with Silver Nanoparticles

Compared to conventional thermal-driven fixation, the light-assisted CO2 fixation into useful chemicals represents a viable strategy for environmental restoratio n and energy sustainability. Hence, in this work, the type of linker was tuned to control the structure and topology of metal–organic frameworks (MOFs), resulting in a diversity of pore networks ranging from two-dimensional (2D) microporous channels (NWU-Cd1, 2) to three-dimensional (3D) nanochannels (NWU-Cd3). Among them, NWU-Cd3 can be employed as a reducing agent to convert Ag(I) ions to Ag(0) to generate Ag/NWU-Cd3 composite materials in situ due to its large pore size, high CO2 adsorption capacity, and redox activity. Ag/NWU-Cd3 can expand the absorption spectrum to the visible area, and it exhibits excellent photocatalytic activity with the yield of styrene carbonate up to 94.3% at light irradiation and room temperature, which is 5.2 times of that under dark conditions. Notably, each Ag NP of the MOF network functions concurrently as a photosensitizer (harvesting light and producing electrons) and a cocatalyst (serving as the Lewis acid). The plasmonic hot electrons can gather on the Ag NP surface under light irradiation and rapidly transfer to NWU-Cd3 to interact with CO2, resulting in activated CO2*. Simultaneously, the presence of Ag NPs provides an action site for epoxides and accelerates the ring-opening process, and thus, Ag/NWU-Cd3 displays high catalytic reactivity for CO2 cycloaddition under mild circumstances (25 °C, 1 atm). This research clarifies the conjunction of light and Ag NPs in accelerating CO2 conversion and offers a substitutable method to further devise effective heterogeneous catalysts for light-induced CO2 cycloaddition.

A nanocaged cadmium-organic framework with high catalytic activity on the chemical fixation of CO2 and deacetalization-knoevenagel condensation

Heterogeneous MOFs catalysts have attracted great attention due to the efficient combination of heterogeneity (easy post-reaction separation and recyclability) and homogeneity (active sites and porosity), which inspire us to explore functional MOFs materials with higher catalytic activity on the chemical fixation of CO2 and deacetalization-Knoevenagel condensation. Herein, the self-assembly of Cd2+ and H6TDP under acidic solvothermal condition generated one cadmium-organic framework of {[(CH3)2NH2]2 [Cd2 (TDP) (H2O)2]⋅3DMF⋅2H2O}n (NUC-29, H6TDP = 2,4,6-tris(2,4-dicarboxyphenyl)pyridine) with nano-caged voids and hierarchical microporous channels, which were built on the combination of two kinds of mononuclear units of [Cd (1) (COO)3(H2O)] and [Cd (2) (COO)3(H2O)]. After the removal of solvent molecules by activation, NUC-29 possesses the coexistence of Lewis acid-base sites on the inner surface of channels including all exposed Cd2+ sites and Npyridine sites, which render it an excellent recyclable heterogeneous catalyst to facilitate the cycloaddition reaction of epoxides with CO2 and deacetalization-Knoevenagel condensation under mild conditions.

Bisligand-coordinated cadmium organic frameworks as fluorescent sensors to detect Ions, antibiotics and pesticides in aqueous solutions

Three bisligand-coordinated two-dimensional or one-dimensional cadmium-based luminescent coordinated polymers, namely, [Cd3(BTC)2(DTP)(H2O)6]·(H2O)2.5 (1) (BTC = benzene-1,3,5-tricarboxylic acid and DTP = 3,5-di(1,2,4-triazol-1-yl)pyridine); [Cd2(IPA)2(DTP)(H2O)4]·(H2O)3(DMF)2 (2) (IPA = isophthalic acid and DMF = dimethylformamide); and [Cd4(DFDA)4(DTP)2(H2O)8]·(H2O)17 (3) (DFDA = 2,5-dihydrofuran-2,5-dicarboxylic acid), were constructed by solvothermal synthesis. The obtained MOFs were characterized by employment of single crystal X-ray diffraction, powder XRD analysis, elemental analysis, IR, TGA and luminescence analysis. Fluorescence sensing experiments show that complexes 1–3 are effective and selective in sensing MnO4−, Fe3+ and Cr2O72−. For the analysis of antibiotics and pesticides, complex 1 exhibited the highest quenching rates for norfloxacin (NOR) and nitenpyram (NTP). For complexes 2–3, cefixime (CFX) and metamitron (MMT) caused the most obvious fluorescence quenching of all of the tested antibiotics and pesticides, respectively. During the sensing processes, both the inner filter effect (IFE) and fluorescence resonance energy transfer (FRET) play a key role in fluorescence quenching for all three complexes.

High Proton Conduction Behavior of a Water-Stable Cadmium Organic Framework and Its Polymer Composite Membranes

A water-stable metal-organic framework material of [Cd2 (pbdc)(H2O)3](1) has been synthesized based on H4pbdc (H4pbdc = 5-phosphonobenzene-1,3-dicarboxylic acid) ligands and Cd2+ ions. The Cd2+ ions are interacted with phosphonate and carboxylate groups to form infinitely extending one-dimensional chains, which are then bridged by pbdc ligands to generate a three-dimensional structure. AC impedance study found that the proton conductivity of compound 1 is 2.32 × 10−4 S·cm−1 at 333 K and 98% RH. Many MOF-polymer composite materials have excellent properties (such as heat resistance, high proton conductivity, etc.) and can be used in fuel cells and other fields. Thus, compound 1 was added to the CS matrix to prepare a series of composite membrane 1@CS-X (X = 1%, 3%, 5%, and 7% wt), which have good thermal stability and high proton conductivity. Under the same conditions, the effects of the 1@CS-X composite membranes on proton conduction are better than that of 1, which is caused by the hydrogen bond network constructed between CS and 1, and that provides a continuous channel for proton transfer. Strikingly, the proton conduction value of 1@CS-3 reached 1.10 × 10−2 S·cm −1 353 K and 98% RH, which is much better than many recently reported MOF-polymer composites.

Retention of a Four-Fold Interpenetrating Cadmium-Organic Framework through a Three-Step Single Crystal Transformation.

Controlled hydration leads to four derivatives of a metal-organic framework consisting of cadmium ions, N1,N1,N4,N4-tetrakis(4-(pyridin-4-yl)phenyl)benzene-1,4-diamine, and coordinated and free nitrates. The balance of water coordination and the multitude of bonding of the weakly coordinated nitrate lead to a progressive change in the coordination number of the Cd2+ ions from eight to seven to six without great perturbation to the 4-fold interpenetration three-dimensional framework.

Recyclable Luminescence Sensor for Dinotefuran in Water by Stable Cadmium-Organic Framework.

Due to the widespread use of dinotefuran around the world, its impact on food and environmental safety has aroused great concern, and the establishment of a rapid and convenient approach for dinotefuran detection is necessary but challenging. Herein, we synthesized a unique three-dimensional framework {[(CH3)2NH2]2[Cd3(BCP)2]·10H2O·3.5DMF}n (1). Single-crystal X-ray analysis indicates that 1 possesses a 4,8-connected anion framework that corresponds to alb topology, with a one-dimensional rectangular channel along the c-axis with the size of 4 Å × 10 Å. Compound 1 displays satisfactory solvent and thermal stability. Luminescent investigations reveal that 1 can selectively detect dinotefuran by fluorescence quenching among other pesticides, displaying excellent anti-interference performance with common ions in water. Importantly, the limit of detection is as low as 2.09 ppm, which is far below the residual concentration of the U.S. food standard. A fluorescence quenching mechanism study shows that there exists competitive energy absorption and static quenching processes. To our knowledge, 1 is the first MOF-based fluorescence probe for dinotefuran detection.

An anionic cadmium-organic framework with an uncommon 3,3,4,8-c network for efficient organic dye separation

A novel anionic metal–organic framework (MOF), {[Cd5(L)4·Na2·(H2O)]·2(CH3)2NH2·3DMF} (LYU-2, Linyi University) (H5L = 2,5-bis(3′,5′-dicarboylphenyl)-benzoic acid), has been solvothermally synthesized and characterized. LYU-2 contains microporous channels with a complicated 3D tetranodal 3,3,4,8-c network, uncoordinated carboxylate groups and coordinated H2O molecules, exhibiting excellent selective adsorption and separation of small cationic dyes through an ion-exchange process in aqueous solution. According to UV/Vis spectroscopy analysis of LYU-2, methylene blue (MB+) and crystal violet (CV+) can be rapidly adsorbed, whereas larger rhodamine B (RB+), anionic methyl orange (MO−), and neutral sudan II (SD0) can hardly be adsorbed. The results imply that the adsorption of dye molecules in LYU-2 displays not only a charge effect, but also a size- and shape-exclusive effect. Furthermore, the adsorbed MB+ can be gradually released in a NaCl-containing aqueous solution.

A double-layered neutral cadmium-organic framework for selective adsorption of cationic organic dyes through electrostatic affinity

The treatment of dyeing wastewater has been a major issue of environmental pollution at present. Adsorption is one of the more feasible methods, Metal-organic frameworks (MOFs) as a class of emerging porous materials have been widely utilized in adsorptive removal of organic dyes. Herein, we designed and synthesized a Cd-MOF {[Cd2(BPTC)(H2O)6]·2H2O}n (H4BPTC ​= ​3,3′,5,5′-biphenyl tetracarboxylic acid) to investigate the correlation of size-exclusion and charge-matching effect between MOFs adsorbents and dye molecules. X-ray single crystal diffraction indicated that Cd-MOF exhibits a unique double-layered helical coordination framework with tetramer water moieties accommodated in the open channels. Zeta-potential of Cd-MOF revealed it a negative charged framework that preferred electrostatic interactions with cationic dye particles, which endorsed Cd-MOF good adsorption capacities to cationic dyes especially methylene blue (MB) with the highest adsorption capacity of 595.4 ​mg ​g–1 at pH ​= ​7.

A new pillared Cd-organic framework as adsorbent of organic dyes and as precursor of CdO nanoparticles

A new neutral cadmium-organic framework with a pillared layer structure, [Cd3(BTC)2(4-bpdb)2] (H3BTC = benzene-1,3,5-tricarboxylic acid; 4-bpdb = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene), has been synthesized via solvothermal reaction of cadmium nitrate with the tricarboxylic acid H3BTC and the linear bispyridyl linker 4-bpdb. The complex has been characterized by single crystal X-ray diffraction, showing to possess a 3D porous network of jcr7 topology. The capability of the prepared MOF in adsorbing the organic dyes Congo Red (CR) and Neutral Red (NR), together with kinetics and thermodynamics of their adsorption, have been investigated in detail. The adsorption process was well described by pseudo-first order and pseudo-second order kinetics for CR and NR, respectively. In addition, conversion of the MOF 3D architecture into nano-sized cadmium oxide particles has also been studied.

Syntheses, structure and properties of an especially stable Cd metal-organic framework driven by benzotriazole-5-carboxylic acid

A new two-dimensional (2D) stable cadmium-organic framework, [Cd(btca)(2,2′-bpy)]n (1), has been successfully designed and synthesized by means of solvothermal method (where H2btca = benzotriazole-5-carboxylic acid, 2,2′-bpy = 2,2′-bipyridine). Complex 1 has been characterized by combining single-crystal X-ray diffraction analysis, elemental analysis and IR spectroscopy. Single-crystal X-ray diffraction analysis reveals that 1 possesses 2D wave-like layered structure, and these 2D wave-like layers are interlinked each other by π-π stacking interactions to form supramolecular network. Compound 1 is especially stable in air, water, acidic/basic aqueous solutions (pH = 1 ~ 13) and common organic solvents. Furthermore, MOF 1 is stable up to 460 °C. Therefore, Compound 1 possesses excellent chemical and thermal stabilities, which makes it possible for practical applications. In addition, the optical property of the complex 1 was investigated.

A stable multifunctional cadmium-organic framework based on 2D stacked layers: Effective gas adsorption, and excellent detection of Cr3+, CrO42−, and Cr2O72-

Multifunctional metal-organic frameworks incorporated with different applications have drawn great attention in chemistry and material science. Herein, a new luminescent compound with 1D microporous channels, namely [Cd(OBA)(L1).0.75DMA]n (1, H2OBA = 4,4′-oxybis(benzoic acid), L1 = 4-amino-3,5-bis(4-pyridyl)-1,2,4-triazole), has been constructed and well explored, which features good thermal and chemical stability. The activated compound 1 with 10.2 Å channels calculated by HK method using N2 adsorption/desorption isotherms at 77 K, reveals a positive CO2 uptake capacity of 68.0 and 40.8 cm3 g−1 at 273 and 298 K, respectively, but it captures a relatively lower amount of CH4 gas under similar atmosphere. Meanwhile, the high H2 capture amount of compound 1 has been demonstrated with 165.2 cm3 g−1 (1.52%) at 1 atm, 77 K. Interestingly, this compound displays a prominently selective and sensitive response to Cr3+, CrO42−, and Cr2O72− in aqueous media. The detection limits of Cr3+, CrO42−, and Cr2O72− are calculated to be 10.25, 0.30, and 9.18 μM, respectively. Moreover, compound 1 can be easily regenerated and reused for detecting CrO42− and Cr2O72− at least three times. Remarkably, the test paper incorporated compound 1 can easily detect these three ions. All these results indicate that compound 1 is a multifunction material with potentials of CO2 selective adsorption and separation, high H2 uptake, high selectivity and sensitivity as well as excellent recyclability for Cr3+, CrO42−, and Cr2O72−.

Bipyridyl-Containing Cadmium-Organic Frameworks for Efficient Photocatalytic Oxidation of Benzylamine.

Metal-organic frameworks (MOFs) have attracted increased research attention in photocatalysis due to their great potential in light harvest and conversion. However, the organic transformations as photocatalyzed by MOFs under mild conditions yet remain a challenge. Herein, three bipyridyl-containing cadmium-organic frameworks Cd(dcbpy) (dcbpy = 2,2'-bipyridine-5,5'-dicarboxylate), Cd(bdc)(bpy) (bdc = 1,4-benzenedicarboxylate; bpy = 2,2'-bipyridyl), and Cd(bdc)(2Me-bpy) (2Me-bpy = 4,4'-dimethyl-2,2'-bipyridyl) were synthesized for the first time. The bpy-containing Cd-MOFs have strong light harvest abilities and suitable photocatalysis energy potentials, making them highly active and selective for the photo-oxidation of benzylamine to N-benzylbenzaldimine under mild conditions, i.e., using atmospheric air as oxidant, at room temperature, and in the absence of any photosensitizer or cocatalyst. It provides an efficient, economical, and green way for the direct oxidation of amines to produce imines.

A Highly Proton-Conductive 3D Ionic Cadmium-Organic Framework for Ammonia and Amines Impedance Sensing.

Lately, the progressive study of metal-organic frameworks (MOFs) for the detection of ammonia and amines has made infusive achievements. Nevertheless, the investigation of proton-conductive MOFs used to detect the low concentrations of ammonia and amine gases at different relative humidities (RHs) at room temperature is relatively restricted. Herein, by solvothermal reaction of Cd(NO3)2 with 2-methyl-1 H-imidazole-4,5-dicarboxylic acid (H3MIDC), a three-dimensional ionic MOF {Na[Cd(MIDC)]} n (1) bearing ordered one-dimensional channels was successfully synthesized. Our research indicates that the uncoordination carboxylate sites are beneficial to proton transfer and the recognition of ammonia and amine compounds. The optimized proton conductivity of 1 reaches a high value of 1.04 × 10-3 S·cm-1 (100 °C, 98% RH). The room temperature sensing properties of ammonia and amine gases were explored under 68, 85, and 98% RHs, respectively. Satisfactorily, the detection limits of MOF 1 toward ammonia, methylamine, dimethylamine, trimethylamine, and ethylamine are 0.05, 0.1, 0.5, 1, and 4 ppm, respectively, which is one of the best room-temperature sensors for ammonia among previous sensors based on proton-conductive MOFs. The proton conducting and sensing mechanisms were highlighted as well.