Halogen bonded three-dimensional uranyl-organic compounds with unprecedented halogen-halogen interactions and structure diversity upon variation of halogen substitution

Actinide-based metal-organic materials have drawn much attention due to their intriguing 5f bonding properties and promising applications in nuclear fuels and other fields. Introduction of weak interactions, such as halogen bonds, into actinide-organic hybrid materials will provide them with more flexibility and dynamics. The first case of halogen bonded three-dimensional (3D) uranyl-organic supramolecular frameworks with regular nanoscale channels has been obtained from multifunctional halogen-substituted isonicotinic acids. Distinct from conventional halogen bonded uranyl-organic frameworks, the supramolecular networks obtained here consist of three-component cocrystals and have been assemblied by intensive supramolecular networks to obtain an extended 3D geometry. Moreover, secondary "X<inf>3</inf> and "X<inf>6</inf>" halogen-halogen interactions resulting from the driving forces of primary hydrogen bonds have been found and analyzed by quantum chemical calculation, indicating their feature of weak bonding and special geometry. It is notable that this unprecedented type of "X<inf>6</inf>" synthon, especially for "Br<inf>6</inf>", represents a new pattern of halogen-halogen interaction. When halogen substitution of the organic precursor is changed, another type of halogen bonded and hydrogen bonded 3D uranyl-organic framework with two-dimensional layered networks and cross-linking agents formed in situ was acquired. Finally, reversible transformation of 3D uranyl-organic supramolecular frameworks is available through loss and regain of water involving in hydrogen bonding networks and thus affords them structural dynamics.