Breathing metal-organic polyhedra controlled by light for carbon dioxide capture and liberation

Metal-organic polyhedra (MOPs) have emerged as versatile platforms for artificial models of biological systems due to their discrete structure and modular nature. However, the design and fabrication of MOPs with special functionality for mimicking biological processes are challenging. Inspired by the breathing mechanism of lungs, we developed a new type of MOP (a breathing MOP, denoted as NUT-101) by directly using azobenzene units as the pillars of the polyhedra to coordinate with Zr-based metal clusters. In addition to considerable thermal and chemical stability, the obtained MOP exhibits photocontrollable breathing behavior. Upon irradiation with visible or UV light, the configuration of azobenzene units transforms, leading to reversible expansion or contraction of the cages and, correspondingly, capture or liberation of CO₂ molecules. Such a breathing behavior of NUT-101 is further confirmed by density functional theory (DFT) calculation. This system might establish an avenue for the construction of new materials with particular functionality that mimic biological processes.