Breathing Metal–Organic Polyhedra Controlled by Light for Carbon Dioxide Capture and Liberation

Abstract

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 CO 2 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.

Multivariate porous platform based on metal-organic polyhedra with controllable functionality assembly

“…Isoreticular series of Zr-based MOPs After screening previously reported MOPs, we selected the Zr-based MOP as a promising candidate for the multivariate platform. Zr-based MOPs display structural robustness and chemical stability, [36][37][38][39][40][41][42][43][44][45][46][47][48][49] two important advantages for synthesis and further characterization. Based on such features, Zr-based MOPs have become an emerging class of porous solids.…”

Surface chemistry of metal–organic polyhedra

“…As in MOFs, the introduction of stimuli-sensitive moieties in the cage backbone in MOPs can yield platforms whose structure responds stimuli such as changes in temperature, light, or solvent. 79 In 2014, Zhou et al synthesised the first example of stimuli-responsive MOP (srMOPs), which they functionalised with azobenzene groups. The cage exhibited UV-irradiation-induced isomerisation from the insoluble trans -conformer to the soluble cis -conformer, whereas irradiation with blue light reversed this process to precipitate out the trans -conformer.…”

Automated Rational Design of Metal–Organic Polyhedra

“…The automated rational proposal of constructible MOPs is not only of synthetic interest, but also in terms of molecular modeling and calculations. Unlike the modeling and calculation of organic cages, we are unaware of accurate calculations on multimetallic MOPs based on force field methods, and thus more computationally demanding DFT approaches may be needed . The latter approach can be very informative in terms of structure and electronic properties, and when a particular target fulfills criteria to be regarded as realistic or “viable”, the predictions of its properties can be suitable for further selection of technologically relevant targets …”