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

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.