Programmable self-assembling 3D architectures generated by patterning of swellable MOF-based composite films

The integration of swellable metal-organic frameworks (MOFs) into polymeric composite films is a straightforward strategy to develop soft materials that undergo reversible shape transformations derived from the intrinsic flexibility of MOF crystals. However, a crucial step toward their practical application relies on the ability to attain specific and programmable actuation, which enables the design of self-shaping objects on demand. Herein, a chemical etching method is demonstrated for the fabrication of patterned composite films showing tunable self-folding response, predictable and reversible 2D-to-3D shape transformations triggered by water adsorption/desorption. These films are fabricated by selective removal of swellable MOF crystals allowing control over their spatial distribution within the polymeric film. Upon exposure to moisture, various programmable 3D architectures, which include a mechanical gripper, a lift, and a unidirectional walking device, are generated. Remarkably, these 2D-to-3D shape transformations can be reversed by light-induced desorption. The reported strategy offers a platform for fabricating flexible MOF-based autonomous soft mechanical devices with functionalities for micromanipulation, automation, and robotics

Surface chemistry of metal-organic polyhedra

This work was funded by the CERCA Programme/Gen-eralitat de Catalunya and through a fellowship (LCF/BQ/PR20/ 11770011) from the "La Caixa" Foundation (ID 100010434).Metal-organic polyhedra (MOPs) are discrete, intrinsically-porous architectures that operate at the molecular regime and, owing to peripheral reactive sites, exhibit rich surface chemistry. Researchers have recently exploited this reactivity through post-synthetic modification (PSM) to generate specialised molecular platforms that may overcome certain limitations of extended porous materials. Indeed, the combination of modular solubility, orthogonal reactive sites, and accessible cavities yields a highly versatile molecular platform for solution to solid-state applications. In this feature article, we discuss representative examples of the PSM chemistry of MOPs, from proof-of-concept studies to practical applications, and highlight future directions for the MOP field

Metal-organic frameworks : from molecules/metal ions to crystals to superstructures

Altres ajuts: I.I. thanks MINECO for a Ramón y Cajal grant.Metal-organic frameworks (MOFs) are among the most attractive porous materials known today, exhibiting very high surface areas, tuneable pore sizes and shapes, adjustable surface functionality, and flexible structures. Advances in the formation of MOF crystals, and in their subsequent assembly into more complex and/or composite superstructures, should expand the scope of these materials in many applications (e.g., drug delivery, chemical sensors, selective reactors and removal devices, etc.) and facilitate their integration onto surfaces and into devices. This Concept article aims to showcase recently developed synthetic strategies to control the one-, two- and three-dimensional (1-, 2- and 3D) organisation of MOF crystals. Superstructures: Recent developments are described for the construction of the first-ever MOF superstructures, all of which entail control over MOF crystallisation and/or the subsequent spatial layout of the resulting crystals. These methods are characterised as 1) spontaneous higher-order assembly, 2) self-assembly using hard templates, 3) self-assembly using soft templates and 4) self-templated synthesis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Optimised room temperature, water-based synthesis of CPO-27-M metal-organic frameworks with high space-time yields

PMCID: PMC4902134The exceptional porosity of Metal-Organic Frameworks (MOFs) could be harnessed for countless practical applications. However, one of the challenges currently precluding the industrial exploitation of these materials is a lack of green methods for their synthesis. Since green synthetic methods obviate the use of organic solvents, they are expected to reduce the production costs, safety hazards and environmental impact typically associated with MOF fabrication. Herein we describe the stepwise optimisation of reaction parameters (pH, reagent concentrations and reaction time) for the room temperature, water-based synthesis of several members of the CPO-27/MOF-74-M series of MOFs, including ones made from Mg(ii), Ni(ii), Co(ii) and Zn(ii) ions. Using this method, we built MOFs with excellent BET surface areas and unprecedented Space-Time Yields (STYs). Employing this approach, we have synthesised CPO-27-M MOFs with record BET surface areas, including 1279 m2 g-1 (CPO-27-Zn), 1351 m2 g-1 (CPO-27-Ni), 1572 m2 g-1 (CPO-27-Co), and 1603 m2 g-1 (CPO-27-Mg). We anticipate that our method could be applied to produce CPO-27-Ni, -Mg, -Co and -Zn with STYs of 44 kg m-3 per day, 191 kg m-3 per day, 1462 kg m-3 per day and a record 18720 kg m-3 per day, respectively.This work was supported by the Spanish MINECO (project PN MAT2012-30994) and the EC (project FP7 ERC-Co 61594). I. I. acknowledges the Spanish MINECO for a Ramón y Cajal grant. ICN2 acknowledges support of the Spanish MINECO through the Severo Ochoa Centres of Excellence Program (Grant SEV-2013-0295).Peer Reviewe

Colloidal metal-organic framework particles : the pioneering case of ZIF-8

The production of metal-organic frameworks (MOFs) in the form of colloids has brought a paradigm shift in the design of new functional porous materials. Along with their intrinsic interest as porous solids, and contrary to their bulk powder counterparts, colloidal MOF particles can additionally be dispersed, shaped, functionalized, transformed and assembled in a controlled manner, conferring them further properties and applications. In this regard, zeolitic imidazolate framework-8 (ZIF-8) has become a pioneering MOF constituent of colloidal science. Today, the understanding of the role of synthetic parameters, learned after one decade of research, enables the production of monodisperse colloidal ZIF-8 particles with tunable dimensions and morphologies, offering the opportunity to develop new functional materials and composites with novel and promising functionalities. This tutorial review provides a useful guide to prepare ZIF-8 in its colloidal form, covering the published studies on the synthesis of homogeneous ZIF-8 particles with controlled size and shape. In addition, we present the most relevant advances in the development of colloidal ZIF-8 hybrid single-particles, reflecting the great potential and rapid development of this interdisciplinary research field. Finally, we highlight how formulation of ZIF-8 as colloids has led to the emergence of novel physicochemical phenomena that are useful for practical applications. This review aims at promoting the development of MOFs as colloids, taking ZIF-8 as a pioneering and successful case that clearly shows the benefits of bridging MOF chemistry and colloidal science

Protection strategies for directionally-controlled synthesis of previously inaccessible metal-organic polyhedra (MOPs) : The cases of carboxylate: The amino-functionalised Rh(ii)-MOPs

Herein we report that strategic use of protecting groups in coordination reactions enables directional inhibition that leads to synthesis of highly functionalised metal-organic polyhedra (MOPs), rather than of the extended coordination networks. Using this approach, we functionalised two new porous cuboctahedral Rh(ii)-based MOPs with 24 peripheral carboxylic acid groups or 24 peripheral amino groups

Protecting metal-organic framework crystals from hydrolytic degradation by spray-dry encapsulating them into polystyrene microspheres

PMCID: PMC4876919Many metal-organic frameworks are water labile, including the iconic Hong-Kong University of Science and Technology-1 (HKUST-1). Spray-dry encapsulation of HKUST-1 crystals into polystyrene microspheres is reported here to yield composites that are resistant to water but retain most of the excellent gas sorption capacity of HKUST-1. These composites are demonstrated to exhibit superior water adsorption/desorption cycling, maintaining the level of water uptake even after three cycles.We thank the MINECO (Spain) for financial support through projects MAT2012-30994, CTQ2011-16009-E and EC FP7 ERC-Co 615954. I.I. thanks the MINECO for a RyC contract and K.C.S. thanks the EU for a Marie Curie Fellowship.Peer Reviewe

Optimised room temperature, water-based synthesis of CPO-27-M metal-organic frameworks with high space-time yields

The exceptional porosity of Metal-Organic Frameworks (MOFs) could be harnessed for countless practical applications. However, one of the challenges currently precluding the industrial exploitation of these materials is a lack of green methods for their synthesis. Since green synthetic methods obviate the use of organic solvents, they are expected to reduce the production costs, safety hazards and environmental impact typically associated with MOF fabrication. Herein we describe the stepwise optimisation of reaction parameters (pH, reagent concentrations and reaction time) for the room temperature, water-based synthesis of several members of the CPO-27/MOF-74-M series of MOFs, including ones made from Mg(ii), Ni(ii), Co(ii) and Zn(ii) ions. Using this method, we built MOFs with excellent BET surface areas and unprecedented Space-Time Yields (STYs). Employing this approach, we have synthesised CPO-27-M MOFs with record BET surface areas, including 1279 m g (CPO-27-Zn), 1351 m g (CPO-27-Ni), 1572 m g (CPO-27-Co), and 1603 m g (CPO-27-Mg). We anticipate that our method could be applied to produce CPO-27-Ni, -Mg, -Co and -Zn with STYs of 44 kg m per day, 191 kg m per day, 1462 kg m per day and a record 18720 kg m per day, respectively

pH-triggered removal of nitrogenous organic micropollutants from water by using metal-organic polyhedra

Altres ajuts: this work funded by the CERCA Programme/Generalitat de Catalunya and through a fellowship (LCF/BQ/PR20/11770011) from the "la Caixa" Foundation (ID 100010434). L.H.L. acknowledges the support from the Spanish State Research Agency (PRE2019-088056).Water pollution threatens human and environmental health worldwide. Thus, there is a pressing need for new approaches to water purification. Herein, we report a novel supramolecular strategy based on the use of a metal-organic polyhedron (MOP) as a capture agent to remove nitrogenous organic micropollutants from water, even at very low concentrations (ppm), based exclusively on coordination chemistry at the external surface of the MOP. Specifically, we exploit the exohedral coordination positions of Rh-MOP to coordinatively sequester pollutants bearing N-donor atoms in aqueous solution, and then harness their exposed surface carboxyl groups to control their aqueous solubility through acid/base reactions. We validated this approach for removal of benzotriazole, benzothiazole, isoquinoline, and 1-napthylamine from water

Steric hindrance in metal coordination drives the separation of pyridine regioisomers using rhodium(II)-based metal-organic polyhedra

Altres ajuts: it was also funded by the CERCA Programme/Generalitat de Catalunya.The physicochemical similarity of isomers makes their chemical separation through conventional techniques energy intensive. Herein, we report that, instead of using traditional encapsulation-driven processes, steric hindrance in metal coordination on the outer surface of Rh-based metal-organic polyhedra (Rh-MOPs) can be used to separate pyridine-based regioisomers via liquid-liquid extraction. Through molecular dynamics simulations and wet experiments, we discovered that the capacity of pyridines to coordinatively bind to Rh-MOPs is determined by the positions of the pyridine substituents relative to the pyridine nitrogen and is influenced by steric hindrance. Thus, we exploited the differential solubility of bound and non-bound pyridine regioisomers to engineer liquid-liquid self-sorting systems. As a proof of concept, we separated four different equimolecular mixtures of regioisomers, including a mixture of the industrially relevant compounds 2-chloropyridine and 3-chloropyridine, isolating highly pure compounds in all cases