Assembly and covalent cross-linking of an amine-functionalised metal-organic cage

The incorporation of reactive functional groups onto the exterior of metal-organic cages (MOCs) opens up new opportunities to link their well-defined scaffolds into functional porous solids. Amine moieties offer access to a rich catalogue of covalent chemistry; however, they also tend to coordinate undesirably and interfere with MOC formation, particular in the case of Cu2 paddlewheel-based MOCs. We demonstrate that tuning the basicity of an aniline-functionalized ligand enables the self-assembly of a soluble, amine-functionalized Cu4L4 lantern cage (1). Importantly, we show control over the coordinative propensity of the exterior amine of the ligand, which enables us to isolate a crystalline, two-dimensional metal-organic framework composed entirely of MOC units (2). Furthermore, we show that the nucleophilicity of the exterior amine of 1 can be accessed in solution to generate a cross-linked cage polymer (3) via imine condensation.Matthew L. Schneider, Adrian W. Markwell-Heys, Oliver M. Linder-Patton and Witold M. Bloc

Charge “mis-matched” hydrogen bonded frameworks for cation exchange and dye sorption

Anionic hydrogen bonded frameworks were synthesised from di or tetra-amidinium hydrogen bond donor components and a charge ‘‘mis-matched’’ tecton possessing a 5 charge but only four hydrogen bond accepting groups. The net negative charge on the framework skeletons necessitates the presence of a cation in the framework channel. In one of the frameworks, the initially incorporated organic cation was rapidly displaced by smaller inorganic cations, or the cationic dye methylene blue. This facilitated the effective and selective removal of this dye from water.Phonlakrit Muang-Non, Adrian W. Markwell-Heys, Christian J. Doonan and Nicholas G. Whit

Self-sorting of porous Cu(4)L(2)L'(2) metal-organic cages composed of isomerisable ligands

We report the self-sorting of a dynamic combinatorial library (DCL) of metal–organic cages composed of a rotationally isomerisable ligand. Convergence of the DCL occurs upon crystallisation and leads to low-symmetry Cu₄L₂L′₂ cages that display differing porosities based on their overall shape and ligand configuration.Adrian W. Markwell-Heys, Matthew L. Schneider, Jenica Marie L. Madridejos, Gregory F. Metha and Witold M. Bloc

Linking metal–organic cages pairwise as a design approach for assembling multivariate crystalline materials

Using metal–organic cages (MOCs) as preformed supermolecular building-blocks (SBBs) is a powerful strategy to design functional metal–organic frameworks (MOFs) with control over the pore architecture and connectivity. However, introducing chemical complexity into the network via this route is limited as most methodologies focus on only one type of MOC as the building-block. Herein we present the pairwise linking of MOCs as a design approach to introduce defined chemical complexity into porous materials. Our methodology exploits preferential Rh-aniline coordination and stoichiometric control to rationally link Cu₄L₄ and Rh₄L₄ MOCs into chemically complex, yet extremely well-defined crystalline solids. This strategy is expected to open up significant new possibilities to design bespoke multi-functional materials with atomistic control over the location and ordering of chemical functionalities.Adrian W. Markwell-Heys, Michael Roemelt, Ashley D. Slattery, Oliver M. Linder-Patton and Witold M. Bloc