Retraction of "Cyclodextrin Metal-Organic Frameworks: From the Research Laboratory to the Marketplace".

Abstract

ConspectusCyclodextrin-based metal-organic frameworks (CD-MOFs), derived from γ-cyclodextrin (γ-CD) and potassium ions, constitute a new class of porous, renewable, and edible MOFs that can be synthesized wholly from naturally occurring starting materials on a large scale. γ-CD is a C8 symmetrical cyclic oligosaccharide, composed of eight asymmetric α-1,4-linked d-glucopyranosyl residues, which possesses a bucket-shaped cavity with an inner diameter of ∼1 nm and a depth of ∼0.8 nm. Upon combining 1 equiv of γ-CD with 8 equiv of potassium hydroxide in aqueous solution, followed by vapor-diffusion of MeOH (or EtOH) into the solution during several days, CD-MOF-1 is obtained as cubic crystals. It was discovered serendipitously in 2010 as the first CD-MOF with a cubic cell of space group I432 and unit cell dimensions of approximately 31 × 31 × 31 Å3. Other CD-MOFs, namely, CD-MOF-2 and CD-MOF-3, can be obtained, respectively, wherein potassium is replaced with rubidium and cesium ions. CD-MOFs comprise infinite body-centered frameworks of (γ-CD)6 cubic units linked by alkali metal cations with spherical pores which reside at the center of the cubes interconnected by both cylindrical and triangular channels.During the past decade, CD-MOFs have emerged as a new class of multifunctional materials based on a porous framework with an extended structure displaying robust crystallinity, permanent porosity, and biocompatibility. The family of CD-MOFs has been enlarged by a growing collection of metal nodes involving alkali metal cations (Li+, Na+, K+, Rb+, Cs+) and γ-CD as well as its derivatives. As a result of the ability of their porous extended frameworks to absorb guest molecules, including gases, drug molecules, metal-based nanoclusters, and nanoparticles, CD-MOFs have potential applications in areas as disparate as adsorption and separation, sensing, template syntheses of metal-based nanoparticles and gels, electrical memory, drug delivery, and catalyst stabilization.In this Account, we tell the story of CD-MOFs, a scientific discovery that was made in our research laboratory at the Northwestern University, and the subsequent commercialization of CD-MOF technology on the part of a spinoff company, which developed a line of successful skin care products. This Account includes representative synthetic methods for the preparation of CD-MOFs, along with a brief overview of their structural features and a general summary of their state-of-the-art applications. The examples, however, are only illustrative, and a significant body of additional findings is emanating from our own laboratory and others, especially in the development of new synthetic strategies, tuning the framework stabilities, and exploring the guest-inclusion properties of CD-MOFs. We refer readers to communications, papers, and reviews on CD-MOFs and to references therein. We also put on record how CD-MOFs have been rebranded as organic molecular vessels (OMVs), a smart, functional, environmentally friendly delivery platform for commercial skin care applications. We hope that, in the telling and retelling of the story of CD-MOFs, this Account may encourage the commercialization of discoveries that have been made in other research laboratories.