Porphyrinic Metal-organic Framework Research Articles

Origamic metal-organic framework toward mechanical metamaterial

Origami, known as paper folding has become a fascinating research topic recently. Origami-inspired materials often establish mechanical properties that are difficult to achieve in conventional materials. However, the materials based on origami tessellation at the molecular level have been significantly underexplored. Herein, we report a two-dimensional (2D) porphyrinic metal-organic framework (MOF), self-assembled from Zn nodes and flexible porphyrin linkers, displaying folding motions based on origami tessellation. A combined experimental and theoretical investigation demonstrated the origami mechanism of the 2D porphyrinic MOF, whereby the flexible linker acts as a pivoting point. The discovery of the 2D tessellation hidden in the 2D MOF unveils origami mechanics at the molecular level.

A Facile One-Pot Synthetic Approach Towards CB@PCN-222(Fe) Composites for Simultaneous Electrochemical Detection of Dihydroxybenzene Isomers

A novel porphyrin-metal organic frameworks (MOFs) based hybrid composite was created by combining conductive carbon black (CB) and PCN-222(Fe) (PCN = porous coordination network) via a one-pot strategy. The proposed material unquestionably takes advantage of the high specific area from MOFs and the strong conductivity of CB, which contributes to the contact with analytes and detection sensitivity. A series of analyses showed that the proposed modified electrode could be an alternative candidate for electrochemical detection of dihydroxybenzene isomers. A good linear correlation occurred between the differential pulse voltammetry current and the concentration of hydroquinone (HQ), catechol (CC) and resorcinol (RC) under the optimized conditions. With low detection limits (0.122, 0.094 and 0.243 μM) at the ranges (0.5–280, 0.5–280 and 0.5–320 μM) of these isomers mentioned above, the sensor exhibited good cost-effectiveness, repeatability and stability. Our methodology drives us to directly analyze the dihydroxybenzene isomers in actual samples with dependable recovery, further broadening the electrochemical detection field for environmental pollutants based on porphyrin MOFs.

A fluorescence analysis model for assessing the water stability of porphyrinic metal−organic frameworks

Porphyrinic metal−organic frameworks (PMOFs) are a type of emerging porous material with potential applications in catalysis, biomedicine, and sensing. Despite their plentiful advantages, the applications of many PMOFs are ultimately limited by their water stability. The water stability of PMOFs is influenced by the coordination interactions between metal nodes and water molecules. In this work, based on the excellent photoluminescent properties of magnesium porphyrins, the interactions between water molecules and PMOFs with 15 metal nodes were studied and assessed by the fluorescence method. First, the ligand-to-metal charge transfer (LMCT) effect of these PMOFs was investigated. Subsequently, according to the fluorescence intensity and kinetic performance of PMOFs in ethanol with different water contents, a model for the water stability of PMOFs was established, and PMOFs were classified into three categories: water stable, relatively stable, and unstable. Finally, the water-sensitive magnesium node PMOF (MgTCPP-Mg) can serve as an excellent fluorescent probe for highly sensitive detection of trace water in organic media, particularly methanol, with detection limits as low as 0.0093 % (v/v). The establishment of this evaluation method and model helps researchers choose the appropriate PMOFs according to their needs.

Aluminum-Porphyrin Metal-Organic Frameworks for Visible-Light Photocatalytic and Sonophotocatalytic Cr(VI) Reduction.

In this study, four isostructural aluminum-based porphyrin metal-organic frameworks [Al-TCPP(M), M = H2 and Zn] with different morphologies and sizes were synthesized by the hydrothermal method. By adjusting the hydrothermal reaction time and the types of porphyrin ligands, Al-TCPP(M) MOFs exhibited diverse morphologies including tetragonal, rectangular, and carambola-like phase. In view of the introduction of porphyrin ligands and the strong coordination effect of Al-O units, Al-TCPP(M) MOFs exhibited good chemical stability, broad visible light harvesting capability, and fast photogenerated charge response. Four Al-TCPP(M) MOFs exhibited excellent photocatalytic activities for Cr(VI) in aqueous solution. Notably, the regulation to the nanoscale carambola-like morphology of Al-TCPP MOFs and metallization of the porphyrin ligand promoted the Cr(VI) photoreduction reaction where the catalytic activity of metallic carambola-like Al-TCPP increased 1.7 times compared to that of nonmetallic tetragonal MOFs. With the assistance of sonophotocatalysis, the Cr(VI) average reduction rates reached 0.658, 0.542, 0.785, and 0.629 mg·L-1·min-1 for Al-TCPP(H2)-24h, Al-TCPP(H2)-72h, Al-TCPP(Zn)-24h, and Al-TCPP(Zn)-72h, which are 1.2-1.4 times higher than that of photocatalysis. UV-vis absorption spectroscopy, electronic spin resonance, and fluorescence spectroscopy experiments demonstrated that the synergistic effect of photochemistry and sonochemistry promoted the transfer of photogenerated electrons from Al-TCPP(M) to Cr(VI), thus enhancing the catalytic activity. The combination of the sonophotocatalytic technology with aluminum-porphyrin MOFs may become an effective strategy to improve MOF-based photocatalytic systems.

A fast hemostatic and enhanced photodynamic 2-dimensional metal-organic framework loaded aerogel patch for wound management

Achieving rapid hemostasis and highly effective antibacterial holds significant importance in the early-stage treatment of wounds. In this study, a hybrid aerogel patch comprising carbon quantum dots (CQDs) modified 2-dimensional (2D) porphyrinic metal–organic framework (MOF) nanosheets was designed by incorporating gelatin methacrylate (GelMA) and polyacrylamide (PAM) based matrix. On one hand, CQDs were stably doped onto the surface of the 2D MOF nanosheets, thereby enhancing the photodynamic activity through fluorescence resonance energy transfer (FRET) process. After the preparation of hybrid aerogel patch, the patch loaded with CQDs-doped 2D MOF exhibited excellent photodynamic bactericidal activity against Gram-positive Staphylococcus aureus (>99.99 %) and Gram-negative Escherichia coli (>99.99 %). On the other hand, the hybrid patch with highly porous and absorbent structure can rapidly absorb blood to aggregate clotting components and form a hydration barrier covering the wound to enhance hemostasis. Besides, the hemolysis and cytotoxicity assays demonstrated a good biocompatibility of this designed patch. In summary, this 2D MOF-loaded aerogel patch holds a potential to achieve rapid hemostasis and effective anti-infection in the early-stage treatment of traumatic wounds.

Colorimetric strategy of Fe/Co-doped porphyrin metal-organic frameworks with enzyme-like activity for the detection of ascorbic acid

The multifunctional structures and functions of metal-organic frameworks with enzyme-like activity make them promising for various applications. This study has shown Fe/Co-doped porphyrin metal-organic framework (PCN-224-Fe/Co) (PCN-224 = porous coordination network-224) efficiently catalyzed the substrates hydrogen peroxide (H2O2) and 3,3′,5,5′-tetramylbenzidine (TMB) to generate oxidized-TMB (oxTMB). The results of the kinetic experiments showed that PCN-224-Fe/Co had a greater affinity for TMB compared to PCN-224-Fe or PCN-224-Co. A selective colorimetric method for determining ascorbic acid (AA) was also successfully developed due to the peroxidase-like activity of PCN-224-Fe/Co. The linear concentration-response range was found to be between 1 and 200 μM with a detection limit of 0.2 μM. This research will facilitate the creation of peroxidase mimics utilizing porphyrin metal-organic frameworks for use in detective applications.

Cooperative Catalytic Alkyne Hydrosilylation by a Porphyrinic Metal-Organic Framework Composite.

Vinylsilanes are valuable building blocks and important structural units in organic chemistry. Herein, catalytic alkyne hydrosilylation was reported to be promoted by a porphyrin metal-organic framework with the incorporation of Pd nanoparticles (Pd@Ir-PCN-222). Catalytic results showed that Pd@Ir-PCN-222 displayed high catalytic efficiency, giving rise to the E isomer vinylsilane with an excellent turnover frequency (TOF) of 2564 h-1. The mechanism studies revealed that the enhancement of the catalytic activity originated from the cooperation between iridium porphyrin and the Pd nanoparticle in confined spaces. The iridium porphyrin was prone to absorb and condense the hydrosilane and alkyne in the inner cavities of Ir-PCN-222, not only accelerating the reaction but also promoting the Pd nanoparticle to activate the Si-H and C≡C bonds of hydrosilane and alkyne, respectively.

Understanding the structure-dependent adsorption behavior of four zirconium-based porphyrinic MOFs for the removal of pharmaceuticals

The adsorptive removal of typical pharmaceuticals, carbamazepine (CBZ) and tetracycline (TC), was investigated with four zirconium-based porphyrinic metal-organic frameworks (MOFs) (PCN-221, PCN-222, PCN-223, and PCN-224). For both CBZ and TC, the adsorption capacities of the PCNs were ranked in the following order: PCN-221 < PCN-223 < PCN-224 < PCN-222. Notably, this order aligns with the BET surface areas of the PCNs. Cage-type PCN-221 showed a lower adsorption capacity than the other three channel-type MOFs due to its small apertures, which were not conducive to the activation of PCN-221 and space utilization. The amount of adsorption was proportional to the cumulative pore volume in PCNs with a width larger than that of the CBZ/TC molecule. Therefore, with high pore volume and large one-dimensional channels formed by ordered linker vacancies, PCN-222 was the best adsorbent in this work. According to the Langmuir model, PCN-222 exhibited exceptional adsorption capacities for CBZ and TC, reaching 305 mg/g and 280 mg/g, respectively. Additionally, the mechanisms for CBZ removal involved hydrogen bonding and π-π interactions/stacking, while electrostatic interactions, hydrogen bonding, and π-π interactions/stacking played crucial roles in TC adsorption onto MOFs. These findings establish a profound comprehension of the interplay between pore structure and performance, providing helpful guidance for designing MOFs to remove emerging contaminants effectively.

A novel nanohybrid constructed by Ti3C2 MXene/TiO2 coupled with porphyrin metal-organic frameworks for enhanced photocatalytic hydrogen production

Highly efficient nanohybrids used in photocatalytic H2 production from water reduction have attracted many attentions in energy conversion and storage of clean energy. Herein, a new dimension-matched nanohybrid was prepared by fabricating two-dimensional copper carboxyphenyl porphyrin metal-organic frameworks (Cu-PMOF) on two-dimensional Ti3C2 MXene/TiO2 nanosheets (TCs). The visible light response and the separation of photoinduced charges in TCs can be efficiently enhanced after coupling with Cu-PMOF. Furthermore, the prepared nanohybrid showed high activity in photocatalytic H2 evolution. Without adding any other co-catalysts, the H2 production over the optimum TCs/Cu-PMOF was 29 times of pure TCs, suggesting the synergetic effect of TCs and Cu-PMOF in the nanocomposite. Moreover, the electron transfer mechanism was explored so as to explain the enhanced activity in the nanohybrid. This study will offer a feasible strategy for fabricating effective nanocomposites used in photocatalysis.

Gelatin‒carboxymethyl cellulose film incorporated porphyrin metal–organic frameworks with photodynamic/photothermal synergistic antibacterial activities for pork packaging application

Gelatin‒carboxymethyl cellulose film incorporated porphyrin metal–organic frameworks with photodynamic/photothermal synergistic antibacterial activities for pork packaging application

Allosteric switch for electrochemical aptasensor toward heavy metals pollution of Lentinus edodes sensitized with porphyrinic metal-organic frameworks

BackgroundLentinan medicament from Lentinus edodes has been considered as natural medicinal products with minimal side effects for cancer therapy, but Lentinus edodes are easily polluted by nonbiodegradable heavy metals, especially silver ion (Ag+). Therefore, it is highly desirable to monitor Ag + pollution in Lentinus edodes considering their adverse impact on lentinan medicament. Electrochemical sensor isn't affected from the interference of matrix turbidity and color, and offers a powerful means for determination of variant analytes. As for electrochemical sensing toward Ag+, there is a great need to design efficient signal probes for specific recognition and signal generation. ResultsWe present an appropriate electrochemical aptasensor for Ag + assay based on biomimetic catalysis of porphyrin-encapsulated MOF (PorMOF) and allosteric switch of C-rich DNA. Thanks to the excellent biocompatibility, PorMOFs as nanozyme are used to design signal probes by loading duplex-like DNA scaffold. Owing to the specific recognition of Ag+ toward cytosine (C) base-rich DNA, PorMOF at the distal end was close to the underlying electrode via C-Ag+-C formation, leading to an enhanced current of catalytic hydroxylamine oxidation for signal generation. Using the positive correlation between current response and Ag+ level, the electrochemical system provides a promising means for on-line monitoring of Ag+ in Lentinus edodes with recoveries from 92.8% to 106.4% and relative standard deviation from 3.98% to 8.24%, verifying the applicability of the electrochemical aptasensor toward Ag+ in Lentinus edodes. Significance and noveltyWith merits of portability, simple operation, and rapid response, the electrochemical pattern offers a useful solution for on-line monitoring of Ag+ in Lentinus edodes. By altering the DNA sequence, the proposed aptasensor provides a powerful way for monitoring other heavy metals, capable of protecting medicament production from heavy metal pollution.

Ultra-stable MOF@MOF nanoplatform for photodynamic therapy sensitized by relieved hypoxia due to mitochondrial respiration inhibition

Metal-organic frameworks (MOFs) with periodically arranged porphyrinic linkers avoiding the self-quenching issue of porphyrins in photodynamic therapy (PDT) have been widely applied. However, the porphyrinic MOFs still face challenges of poor stability under physiological conditions and limited photodynamic efficiency by the hypoxia condition of tumors. Herein, we fabricate the MOF@MOF structure with a protective MOF shell to improve the stability and relieve the hypoxia condition of tumors for sensitized PDT. Under protection of the MOF shell, the MOF@MOF structure can keep intact for 96 h under physiological conditions. Consequently, the tumoral accumulation efficiency is two folds of the MOF core. Furthermore, the MOF shell decomposes under acidic environment, and the loaded inhibitor of mitochondria pyruvate carrier (7-amino carboxycoumarins-2, 7ACC2) will be released. 7ACC2 inhibits the mitochondrial pyruvate influx and simultaneously blocks glucose and lactate from fueling the mitochondrial respiration, thereupon relieving the hypoxia condition of tumors. Under a 5-min laser irradiation, the 7ACC2 carrying MOF@MOF nanoplatforms induced doubled cellular apoptosis and reduced 70% of the tumor growth compared with the cargo-free MOF@MOF. In summary, the design of this stable and hypoxia self-relievable MOF@MOF nanoplatform will enlighten the future development of MOF-based nanomedicines and PDT. Statement of significanceThough widely used for photodynamic therapy (PDT) in previous studies, porphyrinic metal-organic frameworks (MOFs) still face challenges in poor stability under physiological conditions and limited photodynamic efficiency due to the hypoxia condition of tumors. In order to solve these problems, (1) we develop the MOF@MOF strategy to improve the physiological stability; (2) an inhibitor of mitochondria pyruvate carrier, 7-amino carboxycoumarins-2 (7ACC2), is loaded to inhibit the mitochondrial pyruvate influx and simultaneously block glucose and lactate from fueling the mitochondrial respiration, thereupon relieving the hypoxia condition of tumors. In comparison with previous studies, our strategy simultaneously improves stability and overcomes the limited PDT efficiency in the hypoxia tumor tissue, which will enlighten the future development of MOF-based nanomedicines and PDT.

Facile one-pot synthesis of plasmonic gold nanoparticles decorated porphyrin-metal organic framework for photocatalytic hydrogen evolution

Plasmonic metals and single-atom nanocomposites have recently gained attention for their enhancement of photocatalyst ability to harvest energy from visible light photons and consequently increase their photoactivity. Over the last decade, the functionalization of Au nanoparticles has been extensively studied to support photocatalytic processes such as hydrogen generation. Furthermore, porphyrin metal-organic frameworks (MOF) materials have demonstrated promising properties such as high crystallinity, surface area, and electron transfer to favor this reaction. Thus, herein Au@PCN(M) nanocomposite was designed by anchoring surface-modified Au nanoparticles into a porphyrin MOF (PCN(M)) where M represents single-atom transition metals (Pt and Co), these nanocomposites were synthesized by both one-pot and post-synthesis methods. Post-synthesis method displayed a higher yield in comparison to the one-pot method, which could be related to the higher crystallinity and metalation of Co and Pt species on PCN-222. Nevertheless, the obtained results for the one-pot method demonstrated that the developed approach is comparable in terms of performance and is promising for the synthesis of efficient plasmonic photocatalysts and their possibility of scale-up in the future.

The Role of Water in Carbon Dioxide Adsorption in Porphyrinic Metal-Organic Frameworks.

Capturing and converting CO2 through artificial photosynthesis using photoactive, porous materials is a promising approach for addressing increasing CO2 concentrations. Porphyrinic Zr-based metal-organic frameworks (MOFs) are of particular interest as they incorporate a photosensitizer in the porous structure. Herein, the initial step of the artificial photosynthesis is studied: CO2 sorption and activation in the presence of water. A combined vibrational and visible spectroscopic approach was used to monitor the adsorption of CO2 into PCN-222 and PCN-223 MOFs, and the photophysical changes of the porphyrinic linker as a function of water concentration. A shift in CO2 sorption site and bending of the porphyrin macrocycle in response to humidity was observed, and CO2/H2O competition experiments revealed that the exchange of CO2 with H2O is pore-size dependent. Therefore, humidity and pore-size can be used to tune CO2 sorption, CO2 capacity, and light harvesting in porphyrinic MOFs, which are key factors for CO2 photoreduction.

Thermally Induced Orderly Alignment of Porphyrin Photoactive Motifs in Metal-Organic Frameworks for Boosting Photocatalytic CO2 Reduction.

Efficient transfer of charge carriers through a fast transport pathway is crucial to excellent photocatalytic reduction performance in solar-driven CO2 reduction, but it is still challenging to effectively modulate the electronic transport pathway between photoactive motifs by feasible chemical means. In this work, we propose a thermally induced strategy to precisely modulate the fast electron transport pathway formed between the photoactive motifs of a porphyrin metal-organic framework using thorium ion with large ionic radius and high coordination number as the coordination-labile metal node. As a result, the stacking pattern of porphyrin molecules in the framework before and after the crystal transformations has changed dramatically, which leads to significant differences in the separation efficiency of photogenerated carriers in MOFs. The rate of photocatalytic reduction of CO2 to CO by IHEP-22(Co) reaches 350.9 μmol·h-1·g-1, which is 3.60 times that of IHEP-21(Co) and 1.46 times that of IHEP-23(Co). Photoelectrochemical characterizations and theoretical calculations suggest that the electron transport channels formed between porphyrin molecules inhibit the recombination of photogenerated carriers, resulting in high performance for photocatalytic CO2 reduction. The interaction mechanism of CO2 with IHEP-22(Co) was clarified by using in-situ electron paramagnetic resonance, in-situ diffuse reflectance infrared Fourier transform spectroscopy, in-situ extended X-ray absorption fine structure spectroscopy, and theoretical calculations. These results provide a new method to regulate the efficient separation and migration of charge carriers in CO2 reduction photocatalysts and will be helpful to guide the design and synthesis of photocatalysts with superior performance for the production of solar fuels.

Density functional theory–guided electrochemical determination of nitrite in foods based on 2D metal-organic frameworks

This paper presents results for four types of morphology-controlled two-dimensional cobalt based tetrakis (4-carboxyphenyl) porphyrin metal-organic frameworks (2D Co-TCPP MOFs) with different catalytic properties for nitrite, and an electrochemical sensor was fabricated by the Co-TCPP MOF with superior catalytic properties. The sensor exhibited a high sensitivity of 311.3 μg/g, an extra low detection limit (LOD) of 0.03 μM, and a wide linear range of 0.1–375 μM, which was applied successfully for nitrite detection in water, milk and sausage. Moreover, density functional theory (DFT) calculations were used to establish the sensing method, the adsorption structures of nitrite on the surface of Co-TCPP MOF were built and the electrocatalytic mechanism was confirmed. The results explained why the sensor fabricated by a single Co-TCPP MOF exhibited equal or better performance than reported sensors fabricated by composite materials based on a combination of theory and experiment. This work reported a universal electrochemical sensing method for nitrite detection in food based on a single morphology-controlled 2D TCPP MOF, which provided a new and valuable strategy for establishing an efficient food safety determination method guided by theoretical calculations.

Metal ion assistant transformation strategy to synthesize catechol-based metal–organic frameworks from Ti3C2Tx precursors

Chemical transformation strategy is capable of fabricating nanomaterials with well-defined structures and fascinating performance via controllable crystallization kinetics in the phase transformation. V2CTx MXene has been used as precursors to fabricate vanadium porphyrin metal–organic frameworks (V-PMOFs) via the coordination of deprotonated carboxylic acid ligands. However, the rational and in-depth exploration of synthesis mechanism with the aim of enriching the variety of MXene (i.e., Ti3C2Tx) and organic ligands (i.e., catechol-based) to design new MOFs is rarely reported. Herein, we have first developed a metal ion assistant transformation strategy to synthesize three-dimensional catechol-based TiCu-HHTP (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) MOFs with a non-interpenetrating SrSi2 (srs) framework using two-dimensional Ti3C2Tx as precursors. The unique synergetic transformation mechanism involves the electron transfer from Ti3C2Tx to electrostatically adsorbed Cu2+ ion for redox reaction, the subsequent Ti–C bond rupture for Ti4+ ion release, and the continuous chelation coordination between Ti4+/Cu2+ and HHTP. Ti3C2Tx precursors and auxiliary metal ion could be rationally substituted by V2CTx and Mn+ (e.g., Ni2+, Co2+, Mn2+, and Zn2+), respectively. This strategy lays the foundation for the design and synthesis of innovative and multifarious MOFs derived from MXene or other unconventional metal precursors.

A Bimetallic Porphyrin Metal Organic Framework as Multifunctional Catalysts for CO2 Cycloaddition and Alkyne Hydration

AbstractHere, a post synthetic modification strategy is presented to prepare multifunctional Bi−MOF−Co by introducing Co atom into the porphyrin units of bismuth‐porphyrin metal organic framework (Bi−MOF). Under milder conditions (0.1 MPa, 80 °C), CO2 cycloaddition is achieved to form cyclic carbonate in 96 % yield catalyzed by Bi−MOF−Co. The recyclability of catalysts is confirmed by five cycle experiments without loss of activity. Moreover, alkyne hydration is also catalyzed by Bi−MOF−Co in 99 % yield. The hydration protocol exhibites excellent functional group compatibility.

Light‐promoted Selective Reduction of Nitroarenes to Azoxy‐, Azo‐ and Hydrazo‐compounds Catalyzed by Bismuth Porphyrin Metal Organic Framework

AbstractWe report a photocatalytic strategy for selective reduction of nitroarenes to azoxy‐, azo‐ and hydrazo‐compounds catalyzed by bismuth porphyrin metal organic framework (Bi‐MOF) through controlling time, atmosphere, or the quantity of NaBH4 under mild conditions (Rt, Light). The photocatalytic protocol exhibited excellent functional group compatibility, and the recyclability of Bi‐MOF was demonstrated by five cycle tests. More importantly, the scale‐up experiment of 10 g can also be carried out smoothly with excellent yield of 95%. This green and effective photocatalytic strategy provides a practical possibility for the large‐scale synthesis of azo intermediates.

MOF-On-MOF Dual Enzyme-Mimic Nanozyme with Enhanced Cascade Catalysis for Colorimetric/Chemiluminescent Dual-Mode Aptasensing.

A novel metal-organic framework (MOF)-on-MOF dual enzyme-mimic nanozyme was designed as enhanced cascade signal amplification for the colorimetric and chemiluminescent (CL) dual-mode aptasensing. The MOF-on-MOF hybrid is composed of MOF-818 with catechol oxidase-like activity and iron porphyrin MOF [PMOF(Fe)] with peroxidase-like activity, called MOF-818@PMOF(Fe). MOF-818 can catalyze the 3,5-di-tert-butylcatechol substrate and produce H2O2 in situ. Subsequently, PMOF(Fe) catalyzes H2O2 to produce reactive oxygen species, which oxidize 3,3',5,5'-tetramethylbenzidine or luminol to produce color or luminescence. Thanks to the nano-proximity effect and the confinement effect, the efficiency of the biomimetic cascade catalysis is greatly improved, which in turn generates enhanced colorimetric and CL signals. Taking the detection of chlopyrifos as an example, the prepared dual enzyme-mimic MOF nanozyme is combined with the aptamer with specific recognition ability to develop a colorimetric/CL dual-mode aptasensor for highly sensitive and selective detection of chlorpyrifos. The proposed MOF-on-MOF dual nanozyme-enhanced cascade system may provide a new pathway for the further development of a biomimetic cascade sensing platform.