ABSTRACT
An X-ray absorption spectroscopy study of the UiO-67 Pt functionalized metal organic frameworks (MOFs) demonstrates that under appropriate conditions, at least two types of catalytically active sites can be formed in the cavities of the MOF: isolated Pt-complexes and Pt nanoparticles (Pt-NPs). Both pre-made linker synthesis (PMLS) and post-synthesis functionalization (PSF) methods were adopted. XAS was used to monitor the temperature-dependent behaviour of UiO-67-Pt while heating from RT to 623 K, in different gas feeds (pure He, 3% H2/He and 10% H2/He). We collected static in situ Pt LIII XANES and EXAFS spectra at room temperature (RT) before and after the thermal treatment, as well as spectra acquired under operando conditions upon heating. Under 10% H2/He thermal treatment, we unambiguously detected Pt-NP formation which has been followed by a parametric EXAFS analysis of the data collected during temperature programmed H2-reduction (TPR), using the Einstein model to predict the temperature dependence of the Debye-Waller factors. Conversely, in pure He flow, the only significant change observed during TPR is the progressive decrease of the Pt-Cl single scattering contribution, leading to the conclusion that the Pt grafted to the bpydc-linkers remains naked. Advanced EXAFS/TEM analysis allowed us to quantify the fraction of Pt in the form of Pt-NPs, values that have been quantitatively confirmed by linear combination analysis of the XANES spectra. In situ XANES/EXAFS study was supported by ex situ XRPD and BET analyses, confirming the framework stability and testifying a loss of the internal volume after TPR due to the formation of Pt-NPs insides the MOF pores, more relevant in the sample where smaller Pt-NPs were formed.
ABSTRACT
The exceptional thermal and chemical stability of the UiO-66, -67 and -68 classes of isostructural MOFs [J. Am. Chem. Soc., 2008, 130, 13850] makes them ideal materials for functionalization purposes aimed at introducing active centres for potential application in heterogeneous catalysis. We previously demonstrated that a small fraction (up to 10%) of the linkers in the UiO-67 MOF can be replaced by bipyridine-dicarboxylate (bpydc) moieties exhibiting metal-chelating ability and enabling the grafting of Pt(ii) and Pt(iv) ions in the MOF framework [Chem. Mater., 2015, 27, 1042] upon interaction with PtCl2 or PtCl4 precursors. Herein we extend this functionalization approach in two directions. First, we show that by controlling the activation of the UiO-67-Pt we can move from a material hosting isolated Pt(ii) sites anchored to the MOF framework with Pt(ii) exhibiting two coordination vacancies (potentially interesting for C-H bond activation) to the formation of very small Pt nanoparticles hosted inside the MOF cavities (potentially interesting for hydrogenation reactions). The second direction consists of the extension of the approach to the insertion of Cu(ii), obtained via interaction with CuCl2, and exhibiting interesting redox properties. All materials have been characterized by in situ X-ray absorption spectroscopy at the Pt L3- and Cu K-edges.
ABSTRACT
PURPOSE: The new ASCO/CAP guidelines published in 2013 (AC2013) significantly modified the scoring criteria for HER2-FISH, introducing the most controversial change to the HER2-equivocal category. We retrospectively evaluated the impact of AC2013 in a cohort of consecutive invasive breast cancers (IBCs) analyzed with frontline dual-color FISH. METHODS: 2788 consecutive IBCs were reclassified based on the AC2013 guidelines. Clinico-pathological features of equivocal IBCs were compared with HER2-negative and HER2-positive IBCs. FISH HER2-equivocal cases underwent reflex tests: HER2-IHC, RARA-FISH, and SMS-FISH. Overall and disease-free survivals were evaluated in AC2007 HER2-positive patients treated with trastuzumab and in patients that became eligible for target-therapy according to AC2013. RESULTS: Two-hundred HER2-negative cases (7.2%) were classified differently, following AC2013: 0.3% (8/2788) became HER2-positive and 6.9% (192/2788) HER2-equivocal. AC2013, compared with AC2007, significantly increased initial HER2-equivocal cases (6.9%vs1.6%, p < 0.001). AC2013 equivocal-IBCs affected older patients and showed pathological features between HER2-negative and HER2-positive IBCs. After reflex tests, 102 of the 190 equivocal cases (53.7%) were reclassified as HER2-positive, 51 (26.8%) as negative and 37 (19.5%) as equivocal. IHC tested negative in 44.7% of cases, whereas SMS-FISH showed the highest percentage of positive results (45.8%). Clinical outcomes showed no statistically significant differences. CONCLUSION: Overall, 80.5% of FISH-equivocal cases were solved with at least one reflex test and 3.6% of patients became AC2013 HER2-positive, therefore eligible for target-therapy, but showed clinical outcomes similar to HER2-positive patients treated with trastuzumab. Our data belittle the clinical impact of AC2013 HER2-equivocal reclassification; further prospective randomized clinical studies are necessary to support these findings.
