Single-Crystalline\n3D Covalent Organic Frameworks\nwith Exceptionally High Specific Surface Areas and Gas Storage Capacities

Single-crystalline covalent organic frameworks (COFs)\nare highly\ndesirable toward understanding their pore chemistry and functions.\nHerein, two 50–100 μm single-crystalline three-dimensional\n(3D) COFs, TAM-TFPB-COF and TAPB-TFS-COF, were prepared from the condensation\nof 4,4′,4″,4‴-methanetetrayltetraaniline (TAM)\nwith 3,3′,5,5′-tetrakis(4-formylphenyl)bimesityl (TFPB)\nand 3,3′,5,5′-tetrakis(4-aminophenyl)bimesityl (TAPB)\nwith 4,4′,4″,4‴-silanetetrayltetrabenzaldehyde\n(TFS), respectively, in 1,4-dioxane under the catalysis of acetic\nacid. Single-crystal 3D electron diffraction reveals the triply interpenetrated <b>dia-b</b> networks of TAM-TFPB-COF with atom resolution, while\nthe isostructure of TAPB-TFS-COF was disclosed by synchrotron single-crystal\nX-ray diffraction and synchrotron powder X-ray diffraction with Le\nBail refinements. The nitrogen sorption measurements at 77 K disclose\nthe microporosity nature of both activated COFs with their exceptionally\nhigh Brunauer–Emmett–Teller surface areas of 3533 and\n4107 m<sup>2</sup> g<sup>–1</sup>, representing the thus far\nrecord high specific surface area among imine-bonded COFs. This enables\nthe activated COFs to exhibit also the record high methane uptake\ncapacities up to 28.9 wt % (570 cm<sup>3</sup> g<sup>–1</sup>) at 25 °C and 200 bar among all COFs reported thus far. This\nwork not only presents the structures of two single-crystalline COFs\nwith exceptional microporosity but also provides an example of atom\nengineering to adjust permanent microporous structures for methane\nstorage.