A critical bottleneck for the use of natural gas as a transportation fuel has been the development of materials capable of storing it in a sufficiently compact form at ambient temperature. Here we report the synthesis of a porous monolithic metal-organic framework (MOF), which after successful packing and densification reaches 259 cm (STP) cm capacity. This is the highest value reported to date for conformed shape porous solids, and represents a greater than 50% improvement over any previously reported experimental value. Nanoindentation tests on the monolithic MOF showed robust mechanical properties, with hardness at least 130% greater than that previously measured in its conventional MOF counterparts. Our findings represent a substantial step in the application of mechanically robust conformed and densified MOFs for high volumetric energy storage and other industrial applications.

Widespread access to greener energy is required in order to mitigate the effects of climate change. A significant barrier to cleaner natural gas usage lies in the safety/efficiency limitations of storage technology. Despite highly porous metal-organic frameworks (MOFs) demonstrating record-breaking gas-storage capacities, their conventionally powdered morphology renders them non-viable. Traditional powder shaping utilising high pressure or chemical binders collapses porosity or creates low-density structures with reduced volumetric adsorption capacity. Here, we report the engineering of one of the most stable MOFs, Zr-UiO-66, without applying pressure or binders. The process yields centimetre-sized monoliths, displaying high microporosity and bulk density. We report the inclusion of variable, narrow mesopore volumes to the monoliths’ macrostructure and use this to optimise the pore-size distribution for gas uptake. The optimised mixed meso/microporous monoliths demonstrate Type II adsorption isotherms to achieve benchmark volumetric working capacities for methane and carbon dioxide. This represents a critical advance in the design of air-stable, conformed MOFs for commercial gas storage.

As defects significantly affect the properties of metal-organic frameworks (MOFs)-from changing their mechanical properties to enhancing their catalytic ability-obtaining synthetic control over defects is essential to tuning the effects on the properties of the MOF. Previous work has shown that synthesis temperature and the identity and concentration of modulating acid are critical factors in determining the nature and distribution of defects in the UiO family of MOFs. In this paper we demonstrate that the amount of water in the reaction mixture in the synthesis of UiO family MOFs is an equally important factor, as it controls the phase which forms for both and UiO-66(Hf) (F 4 BDC). We use this new understanding of the importance of water to develop a new route to the stable defect-ordered hcp UiO-66(Hf) phase, demonstrating the effectiveness of this method of defect-engineering in the rational design of MOFs. The insights provided by this investigation open up the possibility of harnessing defects to produce new phases and dimensionalities of other MOFs, including nanosheets, for a variety of applications such as MOF-based membranes.Zirconium and hafnium MOFs, including the UiO family, exhibit a wide range of defect chemistry. As defects alter the properties of the framework, obtaining control over the type, location and concentration of defects will in turn allow control over the properties of the MOF. 9,14-17 UiO-66 is an ideal system for study-

Nanoparticle encapsulation inside zirconium-based metal-organic frameworks (NP@MOF) is hard to control and the resulting materials often have non-uniform morphologies with NPs on the external surface of MOFs and NP aggregates inside the MOFs. In this work, we report the controlled encapsulation of gold nanorods (AuNRs) by a scu-topology Zr-MOF, via a room-temperature MOF assembly. This is achieved by functionalizing the AuNRs with polyethylene glycol (PEG) surface ligands, allowing them to retain colloidal stability in the precursor solution and to seed the MOF growth. Using this approach, we achieve core-shell yields exceeding 99%, tuning the MOF particle size via the solution concentration of AuNRs. The functionality of AuNR@MOFs is demonstrated by using the AuNRs as embedded probes for selective surface-enhanced Raman spectroscopy (SERS). The AuNR@MOFs are able to both take-up or block molecules from the pores, thereby facilitating highly-selective sensing at the AuNR ends. This proofof-principle study serves both to present the outstanding level of control in the synthesis as well as the high potential for AuNR@Zr-MOF composites for SERS.

The identification and characterization of low-frequency vibrational motions of metalorganic frameworks (MOFs) allows for a better understanding of their mechanical and structural response upon perturbation by external stimuli such as temperature, pressure, and adsorption. Here, we describe the combination of an experimental temperatureand pressure-dependent terahertz spectroscopy system with quantum mechanical simulations to measure and assign specific low-frequency vibrational modes that directly drive the mechanochemical properties of this important class of porous materials. More specifically, those intense spectral features in the terahertz region of the vibrational spectrum of ZIF-8 are identified, which are directly connected to its mechanochemical response. In particular, the mechanical compressibility of pristine ZIF-8 is found to follow a peculiar non-linear trend upon pressure: its bulk modulus initially increases up to 0.1 GPa and decreases at higher pressures, which is simultaneously reflected in the terahertz vibrational spectra. This work highlights the interplay between structural, vibrational, and mechanochemical phenomena, all of which are key to the effective exploitation of MOFs. The importance of terahertz vibrational motions on the function of MOFs is demonstrated, and a method presented for their measurement and interpretation, which can be applied widely to any supramolecular material.

As defects significantly affect the properties of metal-organic frameworks (MOFs)–from changing their mechanical properties to enhancing their catalytic ability–obtaining synthetic control over defects is essential to tuning the effects on the properties of the MOF. Previous work has shown that synthesis temperature and the identity and concentration of modulating acid are critical factors in determining the nature and distribution of defects in the UiO family of MOFs. In this paper we demonstrate that the amount of water in the reaction mixture in the synthesis of UiO family MOFs is an equally important factor, as it controls the phase which forms for both UiO-67(Hf)<br>and UiO-66(Hf) (F4BDC). We use this new understanding of the importance of water to develop a new route to the stable defect-ordered <b>hcp</b> UiO-66(Hf) phase, demonstrating the effectiveness of this method of defect-engineering in the rational design of MOFs. The insights provided by this<br>investigation open up the possibility of harnessing defects to produce new phases and dimensionalities of other MOFs, including nanosheets, for a variety of applications such as MOF-based membranes.

<div>The identification of low-frequency vibrational motions of metal-organic frameworks (MOFs) allows for a full understanding of their mechanical and structural response upon perturbation by external stimuli such as temperature, pressure, and adsorption. Here, we describe the unique combination of an experimental temperature- and pressure-dependent terahertz spectroscopy system with state-of-the-art quantum mechanical simulation to measure and atomistically assign specific low-frequency vibrational modes that directly drive the mechanochemical properties of this important class of porous materials. Our work highlights the complex interplay between structural, vibrational, and mechanochemical phenomena, all of which are key to the effective exploitation of MOFs. We demonstrate the critical importance of terahertz vibrational motions on the function of MOFs, and how this information can be measured and interpreted in a method that can be applied widely to any supramolecular materials. </div><div><br></div>

As defects significantly affect the properties of metal-organic frameworks (MOFs)–from changing their mechanical properties to enhancing their catalytic ability–obtaining synthetic control over defects is essential to tuning the effects on the properties of the MOF. Previous work has shown that synthesis temperature and the identity and concentration of modulating acid are critical factors in determining the nature and distribution of defects in the UiO family of MOFs. In this paper we demonstrate that the amount of water in the reaction mixture in the synthesis of UiO family MOFs is an equally important factor, as it controls the phase which forms for both UiO-67(Hf)<br>and UiO-66(Hf) (F4BDC). We use this new understanding of the importance of water to develop a new route to the stable defect-ordered <b>hcp</b> UiO-66(Hf) phase, demonstrating the effectiveness of this method of defect-engineering in the rational design of MOFs. The insights provided by this<br>investigation open up the possibility of harnessing defects to produce new phases and dimensionalities of other MOFs, including nanosheets, for a variety of applications such as MOF-based membranes.