Covalent-­Metal-­Organic Frameworks (CMOFs) – 2014


Metal-Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) have emerged as novel crystalline materials with applications in gas storage, sensing and catalysis for example. While the former type of compounds are built upon combining metal centers as structural nodes with polytopic organic ligands, the formation of the latter results from the condensation of purely organic building blocks. We have addressed this issue by the molecular tectonics approach based on the design of programmed molecular tectons and their association into crystalline architectures in the presence of metal centers.

For this strategy, prior to complexation of metal centers, both structural and binding propensity of the organic tecton are coded through its synthesis using non-reversible bond formation processes. Although this has been rather successful, it is, by nature, deterministic.

In this project, we propose to overcome this feature by investigating the possibility of combining reversible bond formation and crystallization processes. This, in principle, should allow to explore a larger landscape by forming libraries of organic- and/or metalla-tectons and their combinations with different metal centers in order to generate coordination polymers of the CMOF type, i.e. crystalline architectures constructed by self-assembly of metal centers or complexes via the formation of reversible covalent bonds instead of purely coordination bond.

As already well established in dynamic combinatorial chemistry, combinations of derivatives bearing complementary reactive groups prone to form reversible covalent bonds lead to complex architectures in equilibrium.
This reversibility may be paralleled with the self-repairing mechanism needed for the formation of crystalline architectures. Thus, one might take advantage of the out-of-equilibrium nature of crystallization to drive the equilibrium process towards the formation of predesigned solid state assemblies. However, this strategy requires a rather fine tuning of the reversible organic condensation kinetics and that of the crystallization event which may be achieved by proper design of experimental condition.