Non-invasive monitoring of the growth of metal-organic frameworks (MOFs) via Raman spectroscopy.

The applicability of Raman spectroscopy for phase discrimination of metal-organic frameworks (MOFs) has been demonstrated with F4_MIL-140A(Ce) and F4_UiO-66(Ce); analogues prepared from the same metal and ligand sources. Each analogue exhibits unique Raman peaks, with significant differences in the low frequency region, which is more sensitive to structural variations. Non-invasive Raman monitoring of F4_MIL-140A(Ce) synthesis indicated evolution of a unique MOF Raman peak with reaction progress; conversion of this Raman signal to extent of crystallisation was in good agreement with reported reaction kinetics determined via a synchrotron diffraction method. Additionally, Raman spectroscopy indicated initial rapid consumption of the nitric acid modulator present in the reaction coinciding with an expected high probability of nucleation. Raman spectroscopy is a promising technique for rapid screening of MOFs and can be used to study the mechanism of their formation in situ with kinetic insight into both the solution and solid phases of the reaction medium.

Blending functionalised ligands to form multivariate metal-organic framework nanosheets (MTV-MONs) with tuneable surface chemistry.

We report a new approach to tuning the properties of metal-organic framework nanosheets (MONs) by blending functionalised ligands to produce multivariate MONs (MTV-MONs). This approach enabled not only fine tuning of the MONs properties, but also resulted in MTV-MONs that show enhanced performance compared to their single-ligand counterparts. Layered copper paddle-wheel based MOFs were synthesised incorporating two or more 2,5-difunctionalised-benzene-1,4-dicarboxylate (fu-BDC) ligands. Liquid ultrasonic exfoliation resulted in the formation of nanosheets down to monolayer thickness presenting multiple functional moieties. Blending of ligands with relatively hydrophilic (methoxy-propoxy) and hydrophobic (pentoxy) moieties resulted in MTV-MONs that showed enhanced dispersion in both polar and apolar solvents compared to either single-ligand parent MON as well as intermediary binding properties. Blending of different fu-BDC ligands with different length alkoxy chains (methoxy-pentoxy) allowed incorporation of up to five different ligands within a single MTV-MON, including ligands which do not form this structure individually. This study demonstrates the potential of blending multiple ligands within an MTV-MON to enable fine-tuning of their structure and properties but also create new nanosheets which are more than the sum of their parts.

Increasing Alkyl Chain Length in a Series of Layered Metal-Organic Frameworks Aids Ultrasonic Exfoliation to Form Nanosheets.

Metal-organic framework nanosheets (MONs) are attracting increasing attention as a diverse class of two-dimensional materials derived from metal-organic frameworks (MOFs). The principles behind the design of layered MOFs that can readily be exfoliated to form nanosheets, however, remain poorly understood. Here we systematically investigate an isoreticular series of layered MOFs functionalized with alkoxy substituents in order to understand the effect of substituent alkyl chain length on the structure and properties of the resulting nanosheets. A series of 2,5-alkoxybenzene-1,4-dicarboxylate ligands (O2CC6H2(OR)2CO2, R = methyl-pentyl, 1-5, respectively) was used to synthesize copper paddle-wheel MOFs. Rietveld and Pawley fitting of powder diffraction patterns for compounds Cu(3-5)(DMF) showed they adopt an isoreticular series with two-dimensional connectivity in which the interlayer distance increases from 8.68 Å (R = propyl) to 10.03 Å (R = pentyl). Adsorption of CO2 by the MOFs was found to increase from 27.2 to 40.2 cm3 g-1 with increasing chain length, which we attribute to the increasing accessible volume associated with increasing unit-cell volume. Ultrasound was used to exfoliate the layered MOFs to form MONs, with shorter alkyl chains resulting in higher concentrations of exfoliated material in suspension. The average height of MONs was investigated by AFM and found to decrease from 35 ± 26 to 20 ± 12 nm with increasing chain length, with the thinnest MONs observed being only 5 nm, corresponding to five framework layers. These results indicate that careful choice of ligand functionalities can be used to tune nanosheet structure and properties, enabling optimization for a variety of applications.

Ultrasonic Exfoliation of Hydrophobic and Hydrophilic Metal-Organic Frameworks To Form Nanosheets.

The modular structure of metal-organic framework nanosheets (MONs) provides a convenient route to creating two-dimensional materials with readily tuneable surface properties. Here, the liquid exfoliation of two closely related layered metal-organic frameworks functionalised with either methoxy-propyl (1) or pentyl (2) pendent groups intended to bestow either hydrophilic or hydrophobic character to the resulting nanosheets is reported. Exfoliation of the two materials in a range of different solvents highlighted significant differences in their dispersion properties, as well as their molecular and nanoscopic structures. Exchange or loss of solvent was found to occur at the labile axial position of the paddle-wheel based MONs and DFT calculations indicated that intramolecular coordination by the oxygen of the methoxy-propyl pendant groups may take place. The nanoscopic dimensions of the MONs were further tuned by varying the exfoliation conditions and through "liquid cascade centrifugation". Aqueous suspensions of the nanosheets were used as sensors to detect aromatic heterocycles with clear differences in binding behaviour observed and quantified.

Dynamic sentinel lymph node biopsy for penile cancer: a comparison between 1- and 2-day protocols.

OBJECTIVE: To determine the outcome of clinically negative node (cN0) patients with penile cancer undergoing dynamic sentinel node biopsy (DSNB), comparing the results of a 1- and 2-day protocol that can be used as a minimal invasive procedure for staging of penile cancer. PATIENTS AND METHODS: This is a retrospective analysis of 151 cN0 patients who underwent DSNB from 2008 to 2013 for newly diagnosed penile cancer. Data were analysed per groin and separated into groups according to the protocol followed. The comparison of the two protocols involved the number of nodes excised, γ-counts, false-negative rates (FNR), and complication rates (Clavien-Dindo grading system). RESULTS: In all, 280 groins from 151 patients underwent DSNB after a negative ultrasound ± fine-needle aspiration cytology. The 1-day protocol was performed in 65 groins and the 2-day protocol in 215. Statistically significantly more nodes were harvested with the 1-day protocol (1.92/groin) compared with the 2-day protocol (1.60/groin). The FNRs were 0%, 6.8% and 5.1%, for the 1-day protocol, 2-day protocol, and overall, respectively. Morbidity of the DSNB was 21.4% for all groins, and 26.2% and 20.1% for the 1-day and 2-day protocols, respectively. Most of the complications were of Clavien-Dindo Grade 1-2. CONCLUSIONS: DSNB is safe for staging patients with penile cancer. There is a trend towards a 1-day protocol having a lower FNR than a 2-day protocol, albeit at the expense of a slightly higher complication rate.