Reticular Synthesis of HKUST-like tbo-MOFs with Enhanced CH₄ Storage

Abstract

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

A Metal–Organic Framework with Optimized Porosity and Functional Sites for High Gravimetric and Volumetric Methane Storage Working Capacities

“…In order to target high volumetric and gravimetric uptakes concurrently, some attempts have been devoted to increase the porosity via systematically elongating the linkers in MOFs with high volumetric uptakes. However, they have been met with very limited success, as exemplified by the HKUST‐like tbo‐MOFs and the ntt‐MOFs . This is because the direct increase in porosity typically correlates to an increase in pore diameters, which can be detrimental to the framework density and strength of methane binding affinity, thus sacrificing the total and working volumetric uptakes .…”

“…However, they have been met with very limited success, as exemplified by the HKUST‐like tbo‐MOFs and the ntt‐MOFs . This is because the direct increase in porosity typically correlates to an increase in pore diameters, which can be detrimental to the framework density and strength of methane binding affinity, thus sacrificing the total and working volumetric uptakes . To overcome this limitation, it is important to maintain or compensate the methane binding strength associated with the surface area/porosity increase in MOFs.…”

“…Interestingly, we found that MOFs with the highest gravimetric (volumetric) uptakes generally exhibit modest volumetric (gravimetric) capacities. This implies that there exists a notably mutual compromise between gravimetric and volumetric capacities for the MOFs, mainly attributed to the opposite relationship between the porosity and CH 4 –framework interactions . However, UTSA‐110a exhibits a notable balance of high volumetric and gravimetric total capacities at RT and 65 bar.…”

Building MOF Nanocomposites with Oxidized Graphitic Carbon Nitride Nanospheres: The Effect of Framework Geometry on the Structural Heterogeneity

“…The diversity of the metal centers and organic ligands leads to materials of particular crystallographic structure, texture, and chemistry. Due to these properties, MOFs have been tested for various applications such as gas separation/storage [4][5][6][7][8][9], purification [10][11][12], sensing [13][14][15][16], electrodes for batteries [17,18], microextraction [19,20], detoxification of chemical warfare agents [21][22][23][24][25], and heterogeneous catalysis [26][27][28].…”

Atomically Dispersed Metal Sites in MOF‐Based Materials for Electrocatalytic and Photocatalytic Energy Conversion

“…We also recommend reports on ADMSs in MOFs for other applications such as organic synthesis and transformation, gas separation, and gas storage for ab roader overview. [53][54][55][56][57][58][59][60][61] Theatomically dispersed open metal sites in MOFs can serve as catalytically active sites for organic reactions.For example,M anna and co-workers functionalized UiO MOFs with atomically dispersed Co/Fe/Mg sites,w hich can efficiently and selectively catalyze ab road range of organic transformations. [53,54] TheADMSs in MOFs can also serve as binding sites for gas adsorption and separation.…”