A spray-drying strategy for synthesis of nanoscale metal–organic frameworks and their assembly into hollow superstructures

TL;DR: The use of spray-drying is reported as a versatile methodology to assemble nanoMOFs, yielding spherical hollow superstructures with diameters smaller than 5 µm, which can be processed into stable colloids, whose disassembly by sonication affords discrete, homogeneous nano MOFs.

Abstract: Metal-organic frameworks (MOFs) are among the most attractive porous materials known today. Their miniaturization to the nanoscale--into nanoMOFs--is expected to serve myriad applications from drug delivery to membranes, to open up novel avenues to more traditional storage and catalysis applications, and to enable the creation of sophisticated superstructures. Here, we report the use of spray-drying as a versatile methodology to assemble nanoMOFs, yielding spherical hollow superstructures with diameters smaller than 5 µm. This strategy conceptually mimics the emulsions used by chemists to confine the synthesis of materials, but does not require secondary immiscible solvents or surfactants. We demonstrate that the resulting spherical, hollow superstructures can be processed into stable colloids, whose disassembly by sonication affords discrete, homogeneous nanoMOFs. This spray-drying strategy enables the construction of multicomponent MOF superstructures, and the encapsulation of guest species within these superstructures. We anticipate that this will provide new routes to capsules, reactors and composite materials.

Summary

Summary

• Miniaturization to the nanometer scale regime is a very prolific strategy for the development of new materials with novel and often enhanced properties compared to traditional materials.
• Today, the growing interest in nanoMOFs demands advanced, low-cost and scalable methodologies for their general synthesis and self-assembly.

Figures

Figure 2. a, Schematic showing the disassembly of the HKUST-1 superstructures upon sonication to form well-dispersed, discrete nanoHKUST-1 crystals. b, Representative FESEM and TEM (insets) images of the HKUST-1 superstructures (b) and corresponding disassembled nanoHKUST-1 crystals (c).

Figure 1. Hollow MOF superstructures obtained by spray-drying.

Full text

A spray-drying strategy for synthesis of nanoscale metal–organic frameworks
and their assembly into hollow superstructures
Inhar Imaz,
1
Arnau Carné,
1
Mary Cano,
1
Daniel Maspoch
1,2
1
CIN2 (ICN-CSIC), Catalan Institute of Nanotechnology, Esfera UAB, 08193 Bellaterra, Spain.
2
Institució Catalana de Recerca i Estudis Avançats (ICREA), 08100 Barcelona, Spain
inhar.imaz@icn.cat, daniel.maspoch@icn.cat
Miniaturization to the nanometer scale regime is a very prolific strategy for the development of new
materials with novel and often enhanced properties compared to traditional materials. In such a context,
nanoscale Metal-Organic Frameworks (also known as nanoMOFs) can also show size-dependent
properties that are expected to expand the scope of MOFs in numerous practical applications, including
drug-delivery, contrast agents, sensor technology and functional membranes and thin-films, while
opening up novel avenues to more traditional storage, separation and catalysis applications and to
functional self-assembled MOF superstructures of
higher complexity.
1
Today, the growing interest in
nanoMOFs demands advanced, low-cost and
scalable methodologies for their general synthesis
and self-assembly. This is crucial if one wants to
start imaging their use for practical applications in a
near future.
Herein, we show that spray-drying technique can be
exploited as a general, low-cost, rapid and scalable
method for the synthesis and self-assembly of
nanoMOFs.
2
It enables massive production of sub-5
µm hollow, spherical MOF superstructures from the
localized crystallization of nanoMOFs on the
surfaces of atomized droplets of a MOF precursor
solution upon heating (Fig. 1). In this method, the atomized droplets produced in spray-drying are used
as individual reactors to confine the fast synthesis and assembly of nanoMOFs at a large scale. The
resulting superstructures are robust and, following disassembly via sonication, afford well-dispersed,
discrete nanoMOFs (Fig. 2).
Importantly, this strategy is applicable to a broad range of MOFs that covers most known porous MOF
subfamilies (HKUST-1, Cu-bdc, NOTT-100, MIL-88A, 43 MIL-88B, MOF-14, MOF-74 [M = Zn(II), Ni(II)
and Mg(II)], UiO-66, ZIF-8, Prussian blue analogues, MOF-5 and IRMOF-3), drastically reduces their
production times and costs, and enables continuous and scalable nanoMOF synthesis as well as
solvent recovery. Furthermore, this spray-drying strategy also enables the construction of MOF
superstructures comprising multiple nanoMOFs assembled together, and the encapsulation of guest
Figure 1. Hollow MOF superstructures obtained by spray-drying.

species, such as fluorescent dyes and inorganic nanoparticles, within these superstructures. We
anticipate that this will provide new routes to capsules, reactors, composite materials, and advanced
adsorbents. As a first proof-of-concept, we show how the entrapment of magnetic nanoparticles within
hollow HKUST-1 superstructures results in advanced adsorbents that can be used for magnetic solid-
phase removal of the organosulfur dibenzothiophene (DBT) fuel contaminant.
References
[1] A. Carné, C. Carbonell, I. Imaz, D. Maspoch, Chem. Soc. Rev. 2011, 40, 291.
[2] A. Carné, I. Imaz, M. Cano-Sarabia, D. Maspoch, Nature Chemistry 2013, DOI: 10.1038/NCHEM.1569.
Figure 2
. a, Schematic showing the disassembly of the HKUST-1 superstructures upon sonication to form well-
dispersed, discrete
n
anoHKUST-1 crystals. b, Representative FESEM and TEM (insets) images of the HKUST-
1 superstructures (b) and corresponding
disassembled nanoHKUST
-1 crystals (c).

Frequently asked questions

Q1. What are the contributions in "A spray-drying strategy for synthesis of nanoscale metal–organic frameworks and their assembly into hollow superstructures" ?

In this paper, the authors proposed a method for the synthesis and self-assembly of nano-MOF superstructures. 

Q2. What is the name of the author?

the growing interest in nanoMOFs demands advanced, low-cost and scalable methodologies for their general synthesis and self-assembly. 

Q3. What is the name of the institute?

2Institució Catalana de Recerca i Estudis Avançats (ICREA), 08100 Barcelona, Spaininhar.imaz@icn.cat, daniel.maspoch@icn.catMiniaturization to the nanometer scale regime is a very prolific strategy for the development of new materials with novel and often enhanced properties compared to traditional materials. 

Q4. What is the method used for the synthesis and assembly of nanoMOFs?

In this method, the atomized droplets produced in spray-drying are used as individual reactors to confine the fast synthesis and assembly of nanoMOFs at a large scale. 

Q5. What is the name of the paper?

In such a context, nanoscale Metal-Organic Frameworks (also known as nanoMOFs) can also show size-dependent properties that are expected to expand the scope of MOFs in numerous practical applications, including drug-delivery, contrast agents, sensor technology and functional membranes and thin-films, while opening up novel avenues to more traditional storage, separation and catalysis applications and tofunctional self-assembled MOF superstructures of higher complexity. 

Q6. Who is the author of this paper?

As a first proof-of-concept, the authors show how the entrapment of magnetic nanoparticles within hollow HKUST-1 superstructures results in advanced adsorbents that can be used for magnetic solidphase removal of the organosulfur dibenzothiophene (DBT) fuel contaminant. 

Q7. What is the name of the authors?

this spray-drying strategy also enables the construction of MOF superstructures comprising multiple nanoMOFs assembled together, and the encapsulation of guestspecies, such as fluorescent dyes and inorganic nanoparticles, within these superstructures.