Metal−organic frameworks (MOFs), such as MOF-74, can have open metal sites to which adsorbates such as CO 2 preferentially bind. 13 C NMR of 13 CO 2 is highly informative about the binding sites present in Mg-MOF-74. We used this technique to investigate loadings between ∼0.88 and 1.15 molecules of CO 2 per metal in Mg-MOF-74 at 295 K. 13 C lineshapes recorded as a function of loading can be understood in terms of the dependence of the CO 2 NMR frequency on the angle (θ) with respect to the CO 2 axis and the channel of the MOF, reflected in the Legendre polynomial, P 2 . In the fast motion limit, the NMR spectra reveal the time-averaged value of P 2 , where θ is the angle between the instantaneous CO 2 axis and the channel axis. DFT calculations were used to determine a weighted average of P 2 in this regime and are in good agreement with experimental data. Static variable temperature 13 C NMR from cryogenic temperatures to room temperature was used to investigate 13 CO 2 binding in Mg-MOF-74 loaded at two levels (∼0.88 and 1.08 molecules of CO 2 per metal), revealing temperature-dependent lineshapes. We have investigated the effect of partial substitution of Cd for Mg in Mg-MOF-74 on the 13 CO 2 variable temperature NMR spectra. The chemical shift anisotropy (CSA) that leads to characteristic lineshapes of 13 C indicates that incorporation of Cd leads to weaker binding energies for adsorbed CO 2 .

The conventional synthesis of metal-organic frameworks (MOFs) through soluble metal-salt precursors provides little control over the growth of MOF crystals. The use of alternative metal precursors would provide a more flexible and cost-effective strategy for direction- and shape-controlled MOF synthesis. Here, we demonstrate for the first time the use of insoluble metal-carbon matrices to foster directed growth of MOFs. Aluminum carbide was implemented as both the metal precursor and growth-directing agent for the generation of MIL-53(Al). A unique needle-like morphology of the MOF was grown parallel to the bulk surface in a layer-by-layer manner. Importantly, the synthesis scheme was found to be transferrable to the production of different linker analogues of the MOF and other topologies. Given the variety of metal carbides available, these findings can be used as a blueprint for controlled, efficient, and economical MOF syntheses and set a new milestone toward the industrial use of MOFs at large-scale.

An in-depth study on the etching process for producing carbide-derived carbons from Al 4 C 3 has been performed. These materials were investigated at a range of etching temperatures from 300 to 900 o C and a range of times from 15 minutes to 6 hours. By altering the etching time and temperature, the surface area, residual aluminum content, and pore size distribution can be turned. A maximum surface area of 1126 m 2 g-1 was observed for materials etched at 500 o C for 1h. The pore size has shown to be tunable from ≤ 0.7 to 8nm. Interestingly, aluminum-based nanoparticles were observed via TEM and SEM for partially etched samples, with evidence of tunable metal species on the surface of the Al 4 C 3-CDC samples at different etching temperatures between 300 and 700 o C. Characterization of the aluminum species present over this temperature range took place using solid-state 27 Al NMR. The formation of crystalline α-Al 2 O 3 was observed at etching temperatures of 700 o C. The results of this work provide detailed synthesis strategies for controlling not only the porosity and surface area of a carbide-derived carbon, but also the extent and type of residual metal nanoparticles embedded in the final structure.

The structure of aluminum carbide (from two different manufacturers) has been interrogated by 27 Al solid-state NMR in an effort to accurately characterize the material. Quadrupolar line shapes for 27 Al sites such as these are important to catalogue, as efforts are underway to employ NMR crystallography tools to understand and predict both solid-state structures and perturbations to these that are relevant to NMR analyses. Impurities present in both of the samples are revealed to be aluminum oxycarbides, as well as an aluminum metal impurity in one and aluminum nitride in anotherpotentially important information for groups employing aluminum carbide in syntheses or in other applications. Triple-quantum magic-angle spinning (3Q-MAS) 27 Al NMR was employed to help determine the quadrupolar parameters of the two crystallographically inequivalent aluminum sites in Al 4 C 3 . Revised values for the quadrupolar tensors of this material were measured and simulated through use of CASTEP-NMR.

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