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

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.