The reported metal–organic framework (MOF) catalyst realizes CO2 to methanol transformation under ambient conditions. The MOF is one rare example containing metal‐free N‐heterocyclic carbene (NHC) moieties, which are installed using an in situ generation strategy involving the incorporation of an imidazolium bromide based linker into the MOF by postsynthetic ligand exchange. Importantly, the resultant NHC‐functionalized MOF is the first catalyst capable of performing quantitative hydrogen transfer from silanes to CO2, thus achieving quantitative (>99 %) methanol yield. Density‐functional theory calculations indicate the high catalytic activity of the NHC sites in MOFs are attributed to the decreased reaction barrier of a reaction route involving the formation of an NHC‐silane adduct. In addition, the MOF‐immobilized NHC catalyst shows enhanced stability for up to eight cycles without base activation, as well as high selectivity towards the desired silyl methoxide product.
Metastasis remains a leading cause of morbidity and mortality from solid tumors. Lack of comprehensive systems to study the progression of metastasis contributes to the low success of treatment. We developed a novel three‐dimensional in vitro reconstructed metastasis (rMet) model that incorporates extracellular matrix (ECM) elements characteristic of the primary (breast, prostate, or lung) and metastatic (bone marrow, BM) sites. A cytokine‐rich liquid interphase separates the primary and distant sites, further recapitulating circulation. Similar to main events underlying the metastatic cascade, the rMet model fractionated human tumor cell lines into sub‐populations with distinct invasive and migratory abilities: (i) a primary tumor‐like fraction mainly consisting of non‐migratory spheroids; (ii) an invasive fraction that invaded through the primary tumor ECM, but failed to acquire anchorage‐independence and reach the BM; and (iii) a highly migratory BM‐colonizing population that invaded the primary ECM, survived in the “circulation‐like” media, and successfully invaded and proliferated within BM ECM. BM‐colonizing fractions successfully established metastatic bone lesions in vivo, whereas the tumor‐like spheroids failed to engraft the bones, showing the ability of the rMet model to faithfully select for highly aggressive sub‐populations with a propensity to colonize a metastatic site. By applying the rMet model to study real‐time ECM remodeling, we show that tumor cells secrete collagenolytic enzymes for invading the primary site ECM but not for entering the BM ECM, indicating possible differences in ECM remodeling mechanisms at primary tumor versus metastatic sites.
A novel advanced oxidation process
(AOP) using ultraviolet/sodium
chlorite (UV/NaClO2) is developed for simultaneous removal
of SO2 and NO. NH4OH, as an additive, was used
to inhibit the generation of ClO2 and NO2. The
removal efficiencies of SO2 and NO reached 98.7 and 99.1%.
NO removal was enhanced by greater UV light intensity and shorter
wavelengths but was insensitive to changes in pH and temperature.
SO2 at 500–1000 mg/m3 improved NO removal,
especially in the absence of UV. The coexistence of SO2 and O2 facilitated the removal of NO by ClO2
–. HCO3
–, Cl–, and Br– enhanced NO removal, but their roles
were negligible when UV was added. The generation of ClO2 and ClO•/HO• was verified by
an UV–vis spectrometer, electron spin resonance (ESR), and
radical-quenching tests. The mechanisms responsible for the removal
of SO2 and NO were attributed to the synergism between
acid–base neutralization and radical-induced oxidation. The
ClO2
– evolution and product composition
were demonstrated by UV–vis and X-ray photoelectron spectroscopy
(XPS). Kinetics analyses showed that the Hatta numbers were 329–798
and 747–1000 without and with UV. Thus, the gas–film
resistance mainly controlled the mass-transfer process.
Six new highly symmetrical and isostructural 3D lanthanide metal-organic frameworks (Ln-MOFs) {[Ln 2 (Ccbp) 3 •6H 2 O]•3Cl − •4H 2 O} Ln = Tb (1), Eu (2), Gd (3), Sm (4), Er (5) and Yb (6), Ccbp − = 4-carboxy-1-(4-carboxybenzyl)pyridinium, and the mixed Ln-MOF {[Tb 1.828 Eu 0.172 7) have been successfully synthesized and fully characterized. The complex 1 was utilized as a representative chemosensor to detect small molecules, cations and anions, respectively. Interestingly, 1 exhibited dualfunctional detection of Pb 2+ and Fe 3+ ions in ethanol with excellent linear variation to quantify the corresponding concentration change. In addition, the temperature-dependent luminescence properties of 1, 2 and 7 have also been investigated systematically, which demonstrated that both 1 and 7 have potential to quantitatively detect temperature as a luminescent thermometer over a wide range from 10-300 K for 1 and 10-170 K for 7. Thus, the as-obtained Ln-MOF materials have potential to serve as the first examples of a multifunctional luminescent sensor for quantitatively detecting the temperature (10-300 K) and the concentration of Pb 2+ and Fe 3+ ions in ethanol solution.
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