Metal−organic frameworks MIL-53(Al)-TDC and MIL-53(Al)-BDC were explored in the SO 2 adsorption process. MIL-53(Al)-TDC was shown to behave as a rigid-like material upon SO 2 adsorption. On the other hand, MIL-53(Al)-BDC exhibits guest-induced flexibility of the framework with the presence of multiple steps in the SO 2 adsorption isotherm that was related through molecular simulations to the existence of three different pore opening phases narrow pore, intermediate pore, and large pore. Both materials proved to be exceptional candidates for SO 2 capture, even under wet conditions, with excellent SO 2 adsorption, good cycling, chemical stability, and easy regeneration. Further, we propose MIL-53(Al)-TDC and MIL-53(A)-BDC of potential interest for SO 2 sensing and SO 2 storage/transportation, respectively.

Monolithic ZIF-8 and ZIF-67 adsorbents are synthesized at room temperature using a novel, ligand-assisted method. Despite reductions in crystallinity within some of the samples, monolithic zeolitic imidazolate frameworks (ZIFs) have superior volume-relative microporosity, total porosity, and surface areas relative to their particulate counterparts due to increased density. Samples synthesized using a single modulator, n-butylamine, have a hierarchical porosity resulting in improved adsorption capacities in mid-to high-sorbate pressure regions. ZIF-67 monoliths produced through mixedmodulator synthesis, n-butylamine and 1-methylimidazole, are almost entirely microporous. Vapor adsorption isotherms find that, whilst their amorphous content results in increased water uptake, monolithic ZIFs are found to possess higher surface and adsorption hydrophobicity than traditional nonpolar adsorbents. Cosorption measurements with a common VOC toluene, under humid conditions, find that these monolithic ZIF samples outperform powder equivalents, with the mixed-modulator ZIF-67 monolith capturing 28% more VOC compared to the powder ZIFs studied due to its superior volumetric efficiency. This study provides insights into the benefits of modulator-based tuning of porosity within monolithic ZIFs which, combined with their hydrophobicity, may facilitate their application for industrial organic vapor recovery or indoor air cleaning, where efficient hydrophobic adsorbents which can operate in humid environments are essential.

DRIFT spectroscopy combined with DFT and QTAIM calculations, revealed the CO preferential adsorption sites within NOTT-401.

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The diffusion processes between adsorbent and adsorbate naturally play a significant role in the efficiency and selectivity of the heterogenous catalytic process. This paper considers the importance of diffusion processes in the transfer hydrogenation reaction of levulinic acid to γ-valerolactone by MIL-88B, MIL-100, and ZIF8@Pd monolithic catalysts. Over a period of five catalytic cycles, it was shown that the Fe-based catalysts can achieve similar conversions to the ZIF-8 supported Pd, with the only current limitation being the lower aqueous stability of these MOFs. Diffusion constants were calculated using the ZLC method, with micropore diffusion limitation found for ZIF-8 and MIL-100 monolithic frameworks at 2.7 x 10−8 and 4.6 x 10−8 cm2 s−1 respectively. This diffusion limitation was also confirmed by IR spectroscopy with an increasing concentration of C—H bands on the MOF substrate post-reaction. Mass transfer coefficients, also calculated by ZLC, revealed increased mass transport for the hydrophobic ZIF-8 framework, which perhaps aids in the γ-valerolactone selectivity over side products that are produced in the absence of catalytic material, as seen for MIL-88B and MIL-100 after multiple uses.