Using Functional Nano- and Microparticles for the Preparation of Metal–Organic Framework Composites with Novel Properties

Abstract

A critical materials challenge over the next quarter century is the sustainable use and management of the world's natural resources, particularly the scarcest of them. Chemistry's ability to get more from less is epitomized by porous coordination polymers, also known as metal-organic frameworks (MOFs), which use a minimum amount of material to build maximum surface areas with fine control over pore size. Their large specific surface area and tunable porosity make MOFs useful for applications including small-molecule sensing, separation, catalysis, and storage and release of molecules of interest. Proof-of-concept projects have demonstrated their potential for environmental applications such as carbon separation and capture, water purification, carcinogen sequestration, byproduct separation, and resource recovery. To translate these from the laboratory into devices for actual use, however, will require synthesis of MOFs with new functionality and structure. This Account summarizes recent progress in the use of nano- and microparticles to control the function, location, and 3D structure of MOFs during MOF self-assembly, creating novel, hybrid, multifunctional, ultraporous materials as a first step towards creating MOF-based devices. The use of preformed ceramic, metallic, semiconductive, or polymeric particles allows the particle preparation process to be completely independent of the MOF synthesis, incorporating nucleating, luminescent, magnetic, catalytic, or templating particles into the MOF structure. We discuss success in combining functional nanoparticles and porous crystals for applications including molecular sieve detectors, repositionable and highly sensitive sensors, pollutant-sequestering materials, microfluidic microcarriers, drug-delivery materials, separators, and size-selective catalysts. In sections within the Account, we describe how functional particles can be used for (1) heterogeneous nucleation (seeding) of MOFs, (2) preparation of framework composites with novel properties, (3) MOF positioning on a substrate (patterning), and (4) synthesis of MOFs with novel architectures.

Fe3O4@HKUST-1 and Pd/Fe3O4@HKUST-1 as magnetically recyclable catalysts prepared via conversion from a Cu-based ceramic

“…32,33 These approaches involve the addition of preformed functional species into the MOF precursor solution and the subsequent in situ formation of MOF crystals with embedded functional particles. Furthermore, it has been demonstrated that the heterospecies can improve the kinetics of MOF formation, [34][35][36] as nano-and micro-particles can act as crystallization facilitators promoting faster MOF growth. On the other hand, functional nanoparticles tend to aggregate under the acidic environment created by the dissociation of ligands during this solution process.…”

General incorporation of diverse components inside metal-organic framework thin films at room temperature

“…Currently, the encapsulation process is widely used to incorporate heteroparticles with new functions into MOFs because the former two methods are limited to covalent bonding and coordination chemistry. Solution impregnation, gas-phase infiltration and solid grinding have been applied to introduce precursors into the preformed MOF host, which is then converted to the corresponding functional components encapsulated in the MOFs 32,33 . However, in this two-step approach, nonselective deposition at the outer surface of the MOF host is unavoidable, and particle size and morphology are limited by the cavities of the MOF host.…”

“…Recently, another more attractive one-pot approach has been developed that involves the addition of preformed functional particles into the MOF precursor solution and the in situ formation of MOF-encapsulated functional particles during MOF growth 33 . However, nanoparticles (NPs) tend to dissolve or agglomerate under the acidic environment created by the dissociation of ligands during this solution process.…”

“…Furthermore, the aforementioned nanoparticles are limited to solid inorganics and polymers that are several to hundreds of nanometres in size 27,[33][34][35][36][37][38][39][40][41][42][43][44] . Hence, the direct encapsulation of ions, inorganic and organic materials as well as bioactive proteins in MOFs at room temperature, without limiting the size, shape and classification and with a short processing time, should ultimately yield functional MOF composite thin films for a wide variety of purposes 47 .…”

Prussian Blue Analogue Mesoframes for Enhanced Aqueous Sodium-ion Storage

“…Therefore, the most widely used approach for the property regulation of coordination polymers is structure design via manipulation of the atomic/molecular packing by intermolecular interactions [13][14][15]. Besides the great success achieved on the molecular/atomic scale, the structure design on a mesoscale (10~1000 nm) has recently been recognized as a promising choice [16][17][18][19]. By downsizing of a bulk crystal, the volume ratio of the surface units to the bulk units can be increased significantly, leading to a coupling effect from the bulk structure and the surface units [17,20,21].…”