Water-Stable etb-MOFs for Methane and Carbon Dioxide Storage

We utilized the etb platform of MOFs for the synthesis of two new water-stable compounds based on amide functionalized trigonal tritopic organic linkers H₃BTBTB (L1), H₃BTCTB (L2) and Al³⁺ metal ions, namely, Al(L1) and Al(L2). The mesoporous Al(L1) material exhibits an impressive methane (CH₄) uptake at high pressures and ambient temperature. The corresponding values of 192 cm³ (STP) cm^-3, 0.254 g g^-1 at 100 bar, and 298 K are among the highest reported for mesoporous MOFs, while the gravimetric and volumetric working capacities (between 80 bar and 5 bar) can be well compared to the best MOFs for CH₄ storage. Furthermore, at 298 K and 50 bar, Al(L1) adsorbs 50 wt % (304 cm³ (STP) cm^-3) CO₂, values among the best recorded for CO₂ storage using porous materials. To gain insight into the mechanism accounting for the resultant enhanced CH₄ storage capacity, theoretical calculations were performed, revealing the presence of strong CH₄ adsorption sites near the amide groups. Our work demonstrates that amide functionalized mesoporous etb-MOFs can be valuable for the design of versatile coordination compounds with CH₄ and CO₂ storage capacities comparable to ultra-high surface area microporous MOFs.