Thermal Stability of Metal–Organic Frameworks and Encapsulation of CuO Nanocrystals for Highly Active Catalysis

Abstract

We report an aerosol-based approach to study the thermal stability of metal-organic frameworks (MOFs) for gas-phase synthesis of MOF-based hybrid nanostructures used for highly active catalysis. Temperature-programmed electrospray-differential mobility analysis (TP-ES-DMA) provides the characterization of temperature-dependent morphological change directly in the gas phase, and the results are shown to be highly correlated with the structural thermal stability of MOFs determined by the traditional measurements of porosity and crystallinity. The results show that MOFs underwent thermal decomposition via simultaneous disassembly and deaggregation. Trimeric Cr-based MIL-88B-NH exhibited a higher temperature of decomposition ( T), 350 °C, than trimeric Fe-based MIL-88B-NH, 250 °C. For UiO-66, a significant decrease of T by ≈100 °C was observed by using amine-functionalized ligands in the MOF structure. Copper oxide nanocrystals were successfully encapsulated in the UiO-66 crystal (Cu O@UiO-66) by using a gas-phase evaporation-induced self-assembly approach followed by a suitable thermal treatment below T (i.e., determined by TP-ES-DMA). Cu O@UiO-66 demonstrated a very high catalytic activity and stability to CO oxidation, showing at least a 3-time increase in CO conversion compared to the bare CuO nanoparticle samples. The study demonstrates a prototype methodology (1) to determine structural thermal stability of MOFs using a gas-phase electrophoretic method (TP-ES-DMA) and (2) to gas-phase synthesize CuO nanocrystals encapsulated in MOFs.

A Gadolinium Metal‐Organic Framework Film as a Converter Layer for Neutron Detection

“…This process was followed by a second 7 % weight loss at approximately 250 °C which corresponds to more tightly bound water or solvent molecules. These two processes correspond to a 22 % weight loss, close to the expected value (22.9 %) for six water molecules coordinated to the Gd 3+ ions in this MOF [19] . Since the obtained phase is a non‐porous 2D structure, no significant amount of solvent is apparently absorbed.…”

Aerobic Homocoupling of Arylboronic Acids Catalyzed by Regenerable Pd(II)@MIL‐88B‐NH2(Cr)

“…Due to the harsh conditions, this method does not become suitable for organic‐based or hybrid materials (such as MOFs) and/or those having lower thermal stability. In this case the calcination temperature needed is higher than the thermal decomposition of Pd(II)@MIL‐88B‐NH 2 (Cr) (T d : 325 °C, see the Supporting Information, Section 2) . For this reason, we aimed to develop a procedure whereby Pd particles could be oxidized and redispersed in the MOF using an oxidant under mild reaction conditions.…”

“…In this case the calcination temperature needed is higher than the thermal decomposition of Pd(II)@MIL-88B-NH 2 (Cr) (T d : 325°C, see the Supporting Information, Section 2). [39] For this reason, we aimed to develop a procedure whereby Pd particles could be oxidized and redispersed in the MOF using an oxidant under mild reaction conditions.…”

Isolating reactive metal-based species in Metal–Organic Frameworks – viable strategies and opportunities

“…Furthermore, these design features are, generally, coupled with a high degree of crystallinity that allows for SCXRD to be used to characterise intermediates and products. 33,39 Compared to molecular crystals, MOFs also provide a high degree of chemical and thermal stability 74 allowing reactions, which might not be tolerated in a crystalline lattice stabilised by intermolecular forces, to occur without host decomposition.…”