Porphyrins and porphyrin derivatives have been widely explored for various applications owing to their excellent photophysical and electrochemical properties. However, inherent shortcomings, such as ...instability and self‐quenching under physiological conditions, limit their biomedical applications. In recent years, metal–organic frameworks (MOFs) have received increasing attention. The construction of porphyrin‐based MOFs by introducing porphyrin molecules into MOFs or using porphyrins as organic linkers to form MOFs can combine the unique features of porphyrins and MOFs as well as overcome the limitations of porphyrins. This Review summarizes important synthesis strategies for porphyrin‐based MOFs including porphyrin@MOFs, porphyrinic MOFs, and composite porphyrinic MOFs, and highlights recent achievements and progress in the development of porphyrin‐based MOFs for biomedical applications in tumor therapy and biosensing. Finally, the challenges and prospects presented by this class of emerging materials for biomedical applications are discussed.
Porphyrin‐based metal–organic frameworks can be designed and constructed for powerful biomedical applications. Recent progress and future expectations are discussed in this Review.
Lithium–sulfur batteries are among the most promising electrochemical energy storage devices of the near future. Especially the low price and abundant availability of sulfur as the cathode material ...and the high theoretical capacity in comparison to state‐of‐the art lithium‐ion technologies are attractive features. Despite significant research achievements that have been made over the last years, fundamental (electro‐) chemical questions still remain unanswered. This review addresses ten crucial questions associated with lithium–sulfur batteries and critically evaluates current research with respect to them. The sulfur–carbon composite cathode is a particular focus, but its complex interplay with other hardware components in the cell, such as the electrolyte and the anode, necessitates a critical discussion of other cell components. Modern in situ characterisation methods are ideally suited to illuminate the role of each component. This article does not pretend to summarise all recently published data, but instead is a critical overview over lithium–sulfur batteries based on recent research findings.
Promising storage: This review addresses ten crucial questions associated with lithium–sulfur batteries and critically evaluates current research with respect to them. The sulfur–carbon composite cathode is in the particular focus, but its complex interplay with other hardware components, such as the electrolyte and the anode, necessitates a critical discussion as well.
Dynamic metal–organic frameworks (MOFs) represent a subgroup of frameworks featuring unique performance, as they are capable of adapting their pore size and/or the orientation of framework ...constituents in response to specific guest molecules such as gases or solutes and often outperform their rigid analogus in gas storage, sensing, or separation. In this review, the authors focus on recent methodical developments of advanced in situ diffraction and spectroscopic techniques for comprehensive characterization of porous frameworks. Examples for advanced instrumentation are highlighted for in situ nuclear magnetic resonance, electron paramagnetic resonance, and optical spectroscopies as well as X‐ray and neutron diffraction. Several examples of high‐resolution transmission electron microscopy (HRTEM) on MOFs are shown because HRTEM is an emerging technique for the characterization of time‐resolved structural dynamics in MOFs. These methods shed light on structural features and phase transitions of the host, its spin state, electronic structure, specific host–guest and guest–guest interactions, preferable adsorption sites, and bonding situation in the framework, focusing on the most prominent recent case studies. The synergistic development of novel in situ characterization methods and exploration of well‐defined model framework systems are crucial to advance the understanding of dynamic processes in porous materials in future.
Structural switchability, accompanied by a large breathing amplitude of the unit cell, is a unique phenomenon in flexible metal–organic frameworks (MOFs). Recent advances in the development of in situ spectroscopic (optical, nuclear magnetic and electron paramagnetic resonance) and diffraction (X‐ray, neutron and electron) techniques for monitoring the dynamic behavior of switchable MOFs upon applying external stimuli are reviewed.
Functionalization of dicarboxylate linkers with proline was used to generate catalytically active metal–organic frameworks (MOFs) for diastereoselective aldol addition. Due to high robustness and ...chemical stability, zirconium based MOFs, namely UiO-67 and UiO-68, were chosen as catalyst hosts. During the MOF synthesis, utilizing Boc protected proline functionalized linkers H2bpdc-NHProBoc and H2tpdc-NHProBoc, in situ deprotection of the Boc groups without racemization is achieved, enabling direct application of the enantiopure, homochiral MOFs in catalytic reaction, without further postsynthetic treatment. Solvent screening and kinetic studies as well as cycling tests were used to evaluate the conditions for diastereoselective aldol addition using a model reaction of 4-nitrobenzaldehyde and cyclohexanone. High yields (up to 97%) were achieved in reasonable reaction time using ethanol as solvent. In comparison to homocatalytic reactions catalyzed by l-proline and its derivatives, MOFs showed opposite diastereoselectivity attributed to the catalytic sites in confined pore space rendering this class of materials as promising catalysts for fine chemicals production.
Rattle‐type Fe3O4@SiO2 hollow mesoporous spheres with different particle sizes, different mesoporous shell thicknesses, and different levels of Fe3O4 content are prepared by using carbon spheres as ...templates. The effects of particle size and concentration of Fe3O4@SiO2 hollow mesoporous spheres on cell uptake and their in vitro cytotoxicity to HeLa cells are evaluated. The spheres exhibit relatively fast cell uptake. Concentrations of up to 150 µg mL−1 show no cytotoxicity, whereas a concentration of 200 µg mL−1 shows a small amount of cytotoxicity after 48 h of incubation. Doxorubicin hydrochloride (DOX), an anticancer drug, is loaded into the Fe3O4@SiO2 hollow mesoporous spheres, and the DOX‐loaded spheres exhibit a somewhat higher cytotoxicity than free DOX. These results indicate the potential of Fe3O4@SiO2 hollow mesoporous spheres for drug loading and delivery into cancer cells to induce cell death.
Hollow mesoporous spheres of Fe3O4@SiO2 exhibit relatively fast cell uptake and no cytotoxicity up to a concentration of 150 µg mL−1 after 48 h of incubation. Doxorubicin hydrochloride (DOX)‐loaded spheres exhibit a somewhat higher cytotoxicity than free DOX (see picture). The Fe3O4SiO2 spheres have potential for drug loading and delivery into cancer cells to induce cell death.
Abstract
Direct electrochemical reduction of CO
2
to fuels and chemicals using renewable electricity has attracted significant attention partly due to the fundamental challenges related to reactivity ...and selectivity, and partly due to its importance for industrial CO
2
-consuming gas diffusion cathodes. Here, we present advances in the understanding of trends in the CO
2
to CO electrocatalysis of metal- and nitrogen-doped porous carbons containing catalytically active M–N
x
moieties (M = Mn, Fe, Co, Ni, Cu). We investigate their intrinsic catalytic reactivity, CO turnover frequencies, CO faradaic efficiencies and demonstrate that Fe–N–C and especially Ni–N–C catalysts rival Au- and Ag-based catalysts. We model the catalytically active M–N
x
moieties using density functional theory and correlate the theoretical binding energies with the experiments to give reactivity-selectivity descriptors. This gives an atomic-scale mechanistic understanding of potential-dependent CO and hydrocarbon selectivity from the M–N
x
moieties and it provides predictive guidelines for the rational design of selective carbon-based CO
2
reduction catalysts.
Herein we developed a targeted anticancer drug delivery system based on folate-conjugated rattle-type Fe3O4@SiO2 hollow mesoporous spheres combining receptor-mediated targeting and magnetic ...targeting. Folic acid (FA) ligands were successfully grafted onto rattle-type Fe3O4@SiO2 hollow mesoporous spheres via amide reaction. The magnetization saturation value of folate-conjugated Fe3O4@SiO2 spheres (Fe3O4@SiO2−FA) was about 1.6 emu/g, and these spheres could be targeted under an external magnetic field. On the other hand, in vitro cytotoxicity and cell uptake of these Fe3O4@SiO2−FA spheres to Hela cells were evaluated. These Fe3O4@SiO2−FA spheres were nontoxic up to a concentration of 150 μg/mL, and further can be specifically taken up by Hela cells via FA receptor-mediated endocytosis. Doxorubicin hydrochloride (DOX), an anticancer drug, was introduced into Fe3O4@SiO2−FA spheres. The release of DOX from Fe3O4@SiO2−FA spheres had a sustained release pattern, and the DOX-loaded Fe3O4@SiO2−FA spheres exhibited greater cytotoxicity than free DOX and DOX-loaded Fe3O4@SiO2 spheres due to the increase of cell uptake of anticancer drug delivery vehicles mediated by the FA receptor. Therefore, we conclude that folate-conjugated Fe3O4@SiO2 hollow mesoporous spheres have potential for targeted anticancer drug delivery for cancer therapy.
A set of porous carbons has been prepared by chemical activation of various fungi-based chars with KOH. The resulting carbon materials have high surface areas (1600–2500m2/g) and pore volumes ...(0.80–1.56cm3/g), regardless of the char precursors. The porosities mainly derived from micropores in activated carbons strongly depend on the activation parameters (temperature and KOH amount). All activated carbons have uniform micropores with pore size of 0.8–0.9nm, but some have a second set of micropores (1.3–1.4nm pore size), further broadened to 1.9–2.1nm as a result of increasing either the activation temperature to 750°C or KOH/char mass ratio to 5/1. These fungi-based porous carbons achieve an excellent H2 uptake of up to 2.4wt% at 1bar and −196°C, being in agreement with results from other porous carbonaceous adsorbents reported in the literature. At high pressure (ca. 35bar), the saturated H2 uptake reaches 4.2–4.7wt% at −196°C for these fungi-based porous carbons. The results imply a great potential of these fungi-based porous carbons as H2 on-board storage media.
Enhancing ionic conductivity of quasi‐solid‐state electrolytes (QSSEs) is one of the top priorities, while conventional metal–organic frameworks (MOFs) severely impede ion migration due to their ...abundant grain boundaries. Herein, ZIF‐4 glass, a subset of MOFs, is reported as QSSEs (LGZ) for lithium‐metal batteries. With lean Li content (0.12 wt%) and solvent amount (19.4 wt%), LGZ can achieve a remarkable ion conductivity of 1.61 × 10−4 S cm−1 at 30 °C, higher than those of crystalline ZIF‐4‐based QSSEs (LCZ, 8.21 × 10−5 S cm−1) and the reported QSSEs containing high Li contents (0.32–5.4 wt%) and huge plasticizer (30–70 wt%). Even at −56.6 °C, LGZ can still deliver a conductivity of 5.96 × 10−6 S cm−1 (vs 4.51 × 10−7 S cm−1 for LCZ). Owing to the grain boundary‐free and isotropic properties of glassy ZIF‐4, the facilitated ion conduction enables a homogeneous ion flux, suppressing Li dendrites. When paired with LiFePO4 cathode, LGZ cell demonstrates a prominent cycling capacity of 101 mAh g−1 for 500 cycles at 1 C with the near‐utility retention, outperforming LCZ (30.7 mAh g−1) and the explored MOF‐/covalent–organic frameworks (COF)‐based QSSEs. Hence, MOF glasses will be a potential platform for practical quasi‐solid‐state batteries in the future.
Glassy metal–organic frameworks with lean Li content (0.12 wt%) and solvent amount (19.4 wt%) show a high ion conductivity, prominent dendritic suppression, and remarkable electrochemical performance when paired with a LiFePO4 cathode, probably due to their isotropic nature and reduced grain boundaries.
A new mesoporous metal–organic framework (MOF; DUT‐60) was conceptually designed in silico using Zn4O6+ nodes, ditopic and tritopic linkers to explore the stability limits of framework architectures ...with ultrahigh porosity. The robust ith‐d topology of DUT‐60 provides an average bulk and shear modulus (4.97 GPa and 0.50 GPa, respectively) for this ultra‐porous framework, a key prerequisite to suppress pore collapse during desolvation. Subsequently, a cluster precursor approach, resulting in minimal side product formation in the solvothermal synthesis, was used to produce DUT‐60, a new crystalline framework with the highest recorded accessible pore volume (5.02 cm3 g−1) surpassing all known crystalline framework materials.
Pores for thought: Computational prediction suggests DUT‐60 as a new framework with sufficient mechanical stability to enable exceptional gas accessible porosity. With an experimentally validated specific surface area of 7839 m2 g−1 and a specific pore volume of 5.02 cm3 g−1 DUT‐60 has the highest ever achieved porosity among all crystalline porous frameworks.
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