(629a) Material Science Meets Rigidity Theory Meets Mechanical Engineering: What Can We Learn About Flexibility of MOFs From the Reduced Topological Representations?

Flexibility of Metal-Organic Frameworks (MOFs) has become one of the most fascinating topics in material science and crystal engineering. Indeed, over the years a number of MOF structures have been discovered that exhibit  a broad and diverse range of conformational effects, from local rotational freedom of linkers to swelling and negative thermal expansion to large amplitude deformations of the framework, such as breathing effects. Given virtually infinite number of possible MOFs, this behaviour can be exploited to develop smart, stimuli responsive, programmable MOFs for controlled drug release, detection and energy storage. Current development of these applications is hindered by poor understanding of the mechanisms of the deformation processes on molecular level.  Here we present a systematic way to detect potential flexibility modes in various classes of MOFs. The approach builds on the reduced topological representations of MOF structures, combined with the rigidity theory analysis. As case studies we consider flexibility modes in IRMOF-1, MIL-53 and several other materials.