The transport of hydrated ions across nanochannels is central to biological systems and membrane-based applications, yet little is known about their hydrated structure during transport due to the absence of in situ characterization techniques. Herein, we report experimentally resolved ion dehydration during transmembrane transport using modified in situ liquid ToF-SIMS in combination with MD simulations for a mechanistic reasoning. Notably, complete dehydration was not necessary for transport to occur across membranes with sub-nanometer pores. Partial shedding of water molecules from ion solvation shells, observed as a decrease in the average hydration number, allowed the alkali-metal ions studied here (lithium, sodium, and potassium) to permeate membranes with pores smaller than their solvated size. We find that ions generally cannot hold more than two water molecules during this sterically limited transport. In nanopores larger than the size of the solvation shell, we show that ionic mobility governs the ion hydration number distribution. Viscous effects, such as interactions with carboxyl groups inside the membrane, preferentially hinder the transport of the mono-and dihydrates. Our novel technique for studying ion solvation in situ represents a significant technological leap for the nanofluidics field and may enable important advances in ion separation, biosensing, and battery applications.
Hydroxyl radical (•OH) can hydroxylate or dehydrogenate organics without forming extra products, thereby expediently applied in extensive domains. Although it can be efficiently produced through single-electron transfer from transition metal-containing activators to hydrogen peroxide (H2O2), narrow applicable pH range, strict activator/H2O2 ratio requirement, and byproducts that are formed in mixture with the background matrix, necessitate the need for additional energy-intensive up/downstream treatments. Here, we show a green Fenton process in an electrochemical cell, where the electro-generated atomic H* on a Pd/graphite cathode enables the efficient conversion of H2O2 into •OH and subsequent degradation of organic pollutants (80% efficiency). Operando liquid time-of-fight secondary ion mass spectrometry verified that the H2O2 activation takes place through a transition state of the Pd-H*-H2O2 adduct with a low reaction energy barrier of 0.92 eV, whereby the lone electron in atomic H* can readily cleave the peroxide bridge, with •OH and H2O as products (∆Gr=-1.344 eV). Using H + or H2O as the resource, we demonstrate that the welldirected output of H* determines the pH-independent production of •OH for stable conversion of organic contaminants in wider pH ranges (3~12). The research pioneers a novel path for eliminating the restrictions that are historically challenging in traditional Fenton process.
Luminescent metal–organic
frameworks (LMOFs) demonstrate
strong potential for a broad range of applications due to their tunable
compositions and structures. However, the methodical control of the
LMOF emission properties remains a great challenge. Herein, we show
that linker engineering is a powerful method for systematically tuning
the emission behavior of UiO-68 type metal–organic frameworks
(MOFs) to achieve full-color emission, using 2,1,3-benzothiadiazole
and its derivative-based dicarboxylic acids as luminescent linkers.
To address the fluorescence self-quenching issue caused by densely
packed linkers in some of the resultant UiO-68 type MOF structures,
we apply a mixed-linker strategy by introducing nonfluorescent linkers
to diminish the self-quenching effect. Steady-state and time-resolved
photoluminescence (PL) experiments reveal that aggregation-caused
quenching can indeed be effectively reduced as a result of decreasing
the concentration of emissive linkers, thereby leading to significantly
enhanced quantum yield and increased lifetime.
While limited choice of emissive organic linkers with systematic emission tunability presents ag reat challenge to investigate energy transfer (ET) over the whole visible light range with designable directions,l uminescent metal-organic frameworks (LMOFs) may serve as an ideal platform for such study due to their tunable structure and composition. Herein, five Zr 6 cluster-based LMOFs,HIAM-400X (X = 0, 1, 2, 3, 4) are prepared using 2,1,3-benzothiadiazole and its derivativebased tetratopic carboxylic acids as organic linkers.T he accessible unsaturated metal sites confer HIAM-400X as apristine scaffold for linker installation. Six full-color emissive 2,1,3-benzothiadiazole and its derivative-based dicarboxylic acids (L) were successfully installed into HIAM-400X matrix to form HIAM-400X-L, in whichthe ET can be facilely tuned by controlling its direction, either from the inserted linkers to pristine MOFs or from the pristine MOFs to inserted linkers, and over the whole range of visible light. The combination of the pristine MOFs and the second linkers via linker installation creates ap owerfult wo-dimensional space in tuning the emission via ET in LMOFs.
We demonstrate the assembly of a
mononuclear metal center, a hexanuclear
cluster, and a V-shaped, trapezoidal tetracarboxylate linker into
a microporous metal–organic framework featuring an unprecedented
3-nodal (4,4,8)-c lyu topology. The compound, HIAM-302,
represents the first example that incorporates both a primary building
unit and a hexanuclear secondary building unit in one structure, which
should be attributed to the desymmetrized geometry of the organic
linker. HIAM-302 possesses optimal pore dimensions and can separate
monobranched and dibranched alkanes through selective molecular sieving,
which is of significant value in the petrochemical industry.
Near-infrared (NIR)-emitting materials have been extensively studied due to their important applications in biosensing and bioimaging. Luminescent metal-organic frameworks (LMOFs) are a new type of highly emissive materials with strong...
Metal–organic
frameworks (MOFs) demonstrate strong potential
for various important applications due to their well tunable structures
and compositions through metal and organic linker engineering. As
an effective approach, topology evolution by controlling linker conformation
has received considerable attention, where solvents and acids have
crucial effects on structural formation. However, a systematic study
of such effects remains under investigated. Herein, we carried out
a methodical study on the topology evolution in Zr-MOFs directed by
solvothermal conditions with various combinations of three common
solvents and six different acids. As a result, three Zr-MOFs with
different topologies, scu (HIAM-4007), scp (HIAM-4008), and csq (HIAM-4009), were obtained using
the same Zr6-cluster and tetratopic carboxylate linker,
in which structure diversity shows significant influence on their
corresponding photoluminescence quantum yields. Further experiments
revealed that the acidity of acids and the basicity of solvents strongly
influenced the linker conformation in the resultant MOFs, leading
to the topology evolution. Such a solvent- and acid-assisted topology
evolution represents a general approach that can be used with other
tetratopic carboxylate linkers to realize structural diversity. The
present work demonstrates an effective structure designing strategy
by controlling synthetic conditions, which may prove to be powerful
for customized synthesis of MOFs with specific structure and functionality.
Luminescent metal-organic frameworks (LMOFs) have been extensively studied for their potential applications in lighting, sensing and biomedicine-related areas due to their high porosity, unlimited structure and composition tunability. However, methodical...
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