Mixed-motif interpenetration and cross-linking of high-connectivity networks led to robust and porous metal–organic frameworks with high gas uptake capacities

Abstract

Two high-connectivity MOFs with very interesting modes of mixed-motif interpenetration and cross-linking were synthesized using the elongated and aromatic-rich methanetetra(biphenyl-p-carboxylic acid) bridging ligand (H₄MTBPC, H₄L). [Zn₄(L)(H₂L)₂]·12DEF·40H₂O (1) contains an interpenetrating 4,8-connected 3D framework of the alb/P topology and 4,4-connected 3D network of the lon topology, whereas [Co₅(L)(HL)₂]·15DMF·37H₂O (2) is the first 4,12-connected 4-nodal net with the Schläfli symbol of {4²².6³⁹.8⁵}{4⁵.6}₂{4⁶}. The structure of 2 can be visualized as cross-linking of three 4,4-connected 3D networks of the lon topology. The seemingly different structures of 1 and 2 are in fact closely related as the structure of 1 can be obtained by removing one of the Co centers in the penta-cobalt secondary building unit (SBU). Unusual mixed-motif interpenetration in 1 and cross-linking in 2 rigidify and stabilize the frameworks, leading to highly porous MOFs with high uptake capacities for H₂ and CO₂.