The chromium terephthalate MIL-101 is a mesoporous metal-organic framework (MOF) with unprecedented adsorption capacities due to the presence of giant pores. The application of an external pressure can effectively modify the open structure of MOFs and its interaction with guest molecules. In this work, we study MIL-101 under pressure by synchrotron X-ray diffraction and infrared (IR) spectroscopy with several pressure transmitting media (PTM). Our experimental results clearly show that when a solid medium as NaCl is employed, an irreversible amorphization of the empty structure occurs at about 0.4 GPa. Using a fluid PTM, as Nujol or high-viscosity silicone oil, results in a slight lattice expansion and a strong modification of the peak frequency and shape of the MOF hydroxyl vibration below 0.1 GPa. Moreover, the framework stability is enhanced under pressure with the amorphization onset shifted to about 7 GPa. This coherent set of results points out the insertion of the fluid inside the MIL-101 pores. Above 7 GPa, concomitantly to the nucleation of the amorphous phase, we observe a peculiar medium-dependent lattice expansion. The behavior of the OH stretching vibrations under pressure is profoundly affected by the presence of the guest fluid, showing that OH bonds are sensitive vibrational probes of the host-guest interactions. The present study demonstrates that even a polydimethylsiloxane silicone oil, although highly viscous, can be effectively inserted into the MIL-101 pores at a pressure below 0.2 GPa. High pressure can thus promote the incorporation of large polymers in mesoporous MOFs.

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The soft nature of organic–inorganic halide perovskites renders their lattice particularly tunable to external stimuli such as pressure, undoubtedly offering an effective way to modify their structure for extraordinary optoelectronic properties. Here, using the methylammonium lead iodide as a representative exploratory platform, it is observed that the pressure‐driven lattice disorder can be significantly suppressed via hydrogen isotope effect, which is crucial for better optical and mechanical properties previously unattainable. By a comprehensive in situ neutron/synchrotron‐based analysis and optical characterizations, a remarkable photoluminescence (PL) enhancement by threefold is convinced in deuterated CD3ND3PbI3, which also shows much greater structural robustness with retainable PL after high peak‐pressure compression–decompression cycle. With the first‐principles calculations, an atomic level understanding of the strong correlation among the organic sublattice and lead iodide octahedral framework and structural photonics is proposed, where the less dynamic CD3ND3+ cations are vital to maintain the long‐range crystalline order through steric and Coulombic interactions. These results also show that CD3ND3PbI3‐based solar cell has comparable photovoltaic performance as CH3NH3PbI3‐based device but exhibits considerably slower degradation behavior, thus representing a paradigm by suggesting isotope‐functionalized perovskite materials for better materials‐by‐design and more stable photovoltaic application.

Metal-organic frameworks (MOFs) are ideal platforms for new and original functionalization as the confinement of metallic nanoparticles (NPs) within their pores. However, the insertion of NPs could impact the framework's mechanical stability thus affecting their performances in applications. Indeed, MOFs are usually loose powders that needs to be compressed to increase the volumetric density before to be employed as gas absorbers. Here, we investigate the high-pressure behavior of the mesoporous MOF MIL-101 loaded with Pd NPs (20, 35 wt%) by synchrotron Xray diffraction and infrared spectroscopy. The control of the metal content allows us to demonstrate that Pd NPs enhance the mechanical stability of MIL-101, with a bulk modulus and a crystallineamorphous transition pressure increasing with the Pd loading. This is attributed to the NPs steric hindrance whereas the presence of host-guest chemical interactions is ruled out by infrared spectroscopy. We also define a spectroscopic quantity highlighting the framework amorphization, that can be exploited from now on to characterize these materials when densified. Our results demonstrate that the incorporation of NPs makes MOFs not only more functional but also more mechanically stable thus suitable for densification.

Hybrid organic–inorganic perovskites (HOIPs) have emerged as outstanding candidates for high-performance photovoltaic devices, and a large variety of HOIPs has been synthesized with different compositions and structural motifs. However, issues remain about their stability and optimization for applications, motivating studies to provide better insight into understanding the structure-property relationship. The application of pressure has proven to be a valuable tool to reach this goal without altering the chemical composition. Indeed, through compression, the atomic and electronic structures of HOIPs can be both finely tuned and dramatically changed, leading to bandgap reduction, phase transitions, and even semiconductor-to-metal transition. In this Perspective, we first provide a general overview of HOIPs, introducing their structure and properties at ambient conditions, focusing only on fully hybrid metal halide perovskites, and thus neglecting the inorganic counterparts. Second, we review and summarize the findings of previous high-pressure research works on these materials, highlighting the common patterns in their high-pressure behavior. We then give an outlook of the main gaps in present work that needs to be filled in our opinion and suggest possible future directions for high-pressure research program on HOIPs. Finally, we provide a first example of such future investigations presenting a preliminary high-pressure low-temperature phase diagram of MAPbBr3 established through synchrotron x-ray diffraction and infrared spectroscopy.

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The infrared absorption spectrum of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI–TfO) was investigated at ambient pressure and variable temperatures between 120 and 330 K, or at room temperature and variable pressures up to 10 GPa. Upon cooling, the ionic liquid crystallizes; on the contrary, upon compression no evidence of crystallization can be obtained from the infrared spectra. Moreover, Density Functional Theory (DFT) calculations were applied to gain a better description of the ionic couple. The ωB97X-D functional, including not only the empirical dispersion corrections but also the presence of a polar solvent, gives a good agreement with the infrared spectrum and suggests that TfO resides above the plane of the imidazolium, with the shorter distance between the O atom of the anion and the C2 atom of the imidazolium ring equal to 2.23 Å.

The π-conjugated, polymer polydiphenylbutadiyne was prepared at the nanoscale confined inside the 1.2 nm 1-D pores of the aluminophosphate AlPO4-54. Molten 1,4-diphenyl-1,3-dibutadiyne (DPB) was inserted in the pores of AlPO4-54...