Successful implementation of reticular chemistry using a judiciously designed rigid octatopic carboxylate organic linker allowed the construction of expanded HKUST-1-like tbo-MOF series with intrinsic strong CH 4 adsorption sites. The Cu-analogue displayed a concomitant enhancement of the gravimetric and volumetric surface area with the highest reported CH 4 uptake among the tbo family, comparable to the best performing MOFs for CH 4 storage. The corresponding gravimetric (BET) and volumetric surface area of 3971 m 2 g -1 and 2363 m 2 cm -3 represent an increase of respectively 115 % and 47 % in comparison to the corresponding values for the prototypical HKUST-1 (tbo-MOF-1), and 42 % and 20 % higher than tbo-MOF-2. High pressure methane adsorption isotherms revealed a high total gravimetric and volumetric CH 4 uptakes, reaching 372 cm 3 (STP) g -1 and 221 cm 3 (STP) cm -3 respectively at 85 bar and 298 K. The corresponding working capacities between 5-80 bar were found to be 294 cm 3 (STP) g -1 and 175 cm 3 (STP) cm -3 and are placed among the best performing MOFs for CH 4 storage particularly at relatively low temperature. To gain insight on the mechanism accounting for the resultant enhanced CH 4 storage capacity, molecular simulation study was performed and revealed the presence of very strong CH 4 adsorption sites near the organic linker with similar adsorption energetics as the open metal sites. The present findings supports the potential of tbo-MOFs based on the supermolecular building layer (SBL) approach as an ideal platform to further enhance the CH 4 storage capacity via expansion and functionalization of the quadrangular pillars. INTRODUCTIONThe utilization of fossil fuels in the energy production and the mobile transportation sector results in the emission of massive amounts of CO 2 in the atmosphere, instigating numerous health and environmental issues. 1 Thus, prompt deployment of environmental friendly fuels is of utmost importance. Natural gas, consisting of nearly 95% CH 4 , is a good candidate for replacing gasoline in mobile transportation and coal in stationary power plants, since it can sustain the same energy demand with amply lessened release of CO, CO 2 , NO x , SO 2 pollutants. 2 Nevertheless, the deployment of methane as a typical fuel in the automotive industry has been hindered by practicalities associated to cost-effective and efficient storage of methane at concrete temperatures and pressures. 3

The ability to direct the assembly of hexagonal building units offers great prospective to construct the awaited and looked-for hypothetical polybenzene (pbz) or "cubic graphite" structure, described 70 years ago. Here, we demonstrate the successful use of reticular chemistry as an appropriate strategy for the design and deliberate construction of a zirconium-based metal-organic framework (MOF) with the intricate pbz underlying net topology. The judicious selection of the perquisite hexagonal building units, six connected organic and inorganic building blocks, allowed the formation of the pbz-MOF-1, the first example of a Zr(IV)-based MOF with pbz topology. Prominently, pbz-MOF-1 is highly porous, with associated pore size and pore volume of 13 Å and 0.99 cm g, respectively, and offers high gravimetric and volumetric methane storage capacities (0.23 g g and 210.4 cm (STP) cm at 80 bar). Notably, the pbz-MOF-1 pore system permits the attainment of one of the highest CH adsorbed phase density enhancements at high pressures (0.15 and 0.21 g cm at 35 and 65 bar, respectively) as compared to benchmark microporous MOFs.

Guest responsive porous materials represent an important and fascinating class of multifunctional solids that have attracted considerable attention in recent years. An understanding of how these structures form is essential toward their rational design, which is a prerequisite for the development of tailor-made materials for advanced applications. We herein report a novel series of stable rare-earth (RE) MOFs that show a rare continuous breathing behavior and an unprecedented gas-trapping property. We used an asymmetric 4-c tetratopic carboxylate-based organic ligand that is capable of affording highly crystalline materials upon controlled reaction with RE cations. These MOFs, denoted as RE-thc-MOF-1 (RE: Y3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, and Er3+), feature hexanuclear RE6 clusters that display a highly unusual connectivity and serve as unique 8-c hemi-cuboctahedral secondary building block, resulting in a new (3,3,8)-c thc topology. Extensive single-crystal to single-crystal structural analyses coupled with detailed gas (N2, Ar, Kr, CO2, CH4, and Xe) and vapor (EtOH, CH3CN, C6H6, and C6H14) sorption studies, supported by accurate theoretical calculations, shed light onto the unique swelling behavior. The results reveal a synergistic action involving steric effects, associated with coordinated solvent molecules and 2-fluorobenzoate (2-FBA) nonbridging ligands, as well as cation–framework electrostatic interactions. We were able to probe the individual role of the coordinated solvent molecules and 2-FBA ligands and found that both cooperatively control the gas-breathing and -trapping properties, while 2-FBA controls the vapor adsorption selectivity. These findings provide unique opportunities toward the design and development of tunable RE-based flexible MOFs with tailor-made properties.

Ligand modification in MOFs provides great opportunities not only for the development of functional materials with new or enhanced properties but also for the discovery of novel structures. We report here that a sulfone-functionalized tetrahedral carboxylate-based ligand is capable of directing the formation of new and fascinating MOFs when combined with Zr 4+ /Hf 4+ and rare-earth metal cations (RE) with improved gas-sorption properties. In particular, the resulting M-flu-SO 2 (M: Zr, Hf) materials display a new type of the augmented flu-a net, which is different as compared to the flu-a framework formed by the nonfunctionalized tetrahedral ligand. In terms of properties, a remarkable increase in the CO 2 uptake is observed that reaches 76.6% and 61.6% at 273 and 298 K and 1 bar, respectively. When combined with REs, the sulfone-modified linker affords novel MOFs, REhpt-MOF-1 (RE: Y 3+ , Ho 3+ , Er 3+ ), which displays a fascinating (4, 12)coordinated hpt net, based on nonanuclear [RE 9 (μ 3 -Ο) 2 (μ 3 -ΟΗ) 12 (−COO) 12 ] clusters that serve as hexagonal prismatic building blocks. In the absence of the sulfone groups, we discovered that the tetrahedral linker directs the formation of new RE-MOFs, RE-ken-MOF-1 (RE: Y 3+ , Ho 3+ , Er 3+ , Yb 3+ ), that display an unprecedented (4, 8)-coordinated ken net based on nonanuclear RE 9 -clusters, to serve as bicapped trigonal prismatic building units. Successful activation of the representative member Y-ken-MOF-1 reveals a high BET surface area and total pore volume reaching 2621 m 2 g −1 and 0.95 cm 3 g −1 , respectively. These values are the highest among all RE MOFs based on nonanuclear clusters and some of the highest in the entire RE family of MOFs. The present work uncovers a unique structural diversity existing between Zr/ Hf and RE-based MOFs that demonstrates the crucial role of linker design. In addition, the discovery of the new RE-hpt-MOF-1 and RE-ken-MOF-1 families of MOFs highlights the great opportunities existing in RE-MOFs in terms of structural diversity that could lead to novel materials with new properties.

Epoxy terpenes cyclize readily, by confinement within zeolite NaY, to form exomethylenic cyclohexanols as the major products. The selective monocyclization of 10,11-epoxyfarnesyl acetate within NaY provides a short and efficient biomimetic route to (+/-)-elengasidiol and (+/-)-farnesiferols B-D. [reaction: see text].