Structural Evolution from Noninterpenetrated to Interpenetrated Thorium–Organic Frameworks Exhibiting High Propyne Storage

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Two thorium–organic frameworks of [Th 6 O 4 (OH) 4 (TFBPDC) 6 (H 2 O) 6 ] n ( Th-TFBPDC ) and [Th 6 O 4 (OH) 4 (TFBPDC) 4 (HCOO) 4 (H 2 O) 6 ] n ( Th-TFBPDC-i ) constructed from the 3,3′,5,5′-tetrakis(fluoro)biphenyl-4,4′-dicarboxylate (TFBPDC 2– ) ligand were obtained in a reaction. At an early stage of the reaction, the formation of the three-dimensional (3D) framework of Th-TFBPDC was discovered. At a later stage of the reaction, the complete product of Th-TFBPDC-i was obtained. The structural evolution from a noninterpenetrated network of Th-TFBPDC to a 2-fold interpenetrated network of Th-TFBPDC-i is a dissolution–recrystallization process and rationalized as the four equatorial TFBPDC 2– ligands in an octahedral [Th 6 O 4 (OH) 4 (TFBPDC) 12 ] unit were displaced by four formate ligands to form a [Th 6 O 4 (OH) 4 (TFBPDC) 8 (HCOO) 4 ] unit via a ligand substitution reaction. The large pore volume as well as the strong interactions between the host framework and guest propyne (C 3 H 4 ) molecules demonstrated by computational results endow the highly water-stable Th-TFBPDC with the best-performing C 3 H 4 storage under ambient conditions. This work presents a rare example of structural evolution from a 3D noninterpenetrated network to a 2-fold 3D interpenetrated network and a highly promising metal–organic framework (MOF) for C 3 H 4 storage with a C 3 H 4 uptake of 8.16 mmol g –1 at 298 K.