Nanoporous materials

Research fields in the area of nanoporous materials include imprinted polymers which can function according to the lock-and-key principle, thus enabling the development of (for example) selective sensors, and metal-organic framework structures, for example for applications in the areas of gas storage, separation techniques and sensor technology. Current research projects include the EU/BMBF project "SENSIndoor" and the Fraunhofer cooperation "MOF2market".

Molecularly imprinted polymers

Molecular Imprinted Polymers
© Photo Fraunhofer ICT
© Photo Fraunhofer ICT

Molecular polymer imprinting is a highly elegant and efficient method of producing functional materials equipped with selective identification characteristics. Using the lock-and-key principle, selective materials can be produced for different applications, such as sensors, purification of mixtures or enrichment.

Advantages and applications

Molecularly imprinted polymers (MIPs) are produced by synthesizing highly cross-linked polymers in the presence of template molecules. In a self-organizing process, the growing polymer skeleton adapts to the molecular model, forming a type of imprint of the molecular template. The geometric adaptation of the polymer and the interactions of the functional groups, for example the formation of hydrogen bonds, make the polymer selective for the template, which means that it can be applied as a selective sensor coating.

At Fraunhofer ICT, MIPs are being developed as sensor coatings for the detection of explosives, and as particles for the enrichment of semi-volatile compounds. Various coating technologies such as nanoplotting, spin coating, screen printing and various synthesis methods (UV polymerization, suspension polymerization, core-shell particles are used. Possible analytes range from explosives or toxic substances, such as herbicides and pesticides, to natural substances such as steroids.

Our offer

  • Synthesis of MIP materials for customer-specific target molecules for enrichment / extraction or as selective sensor coatings
  • Adjustment or development of coating processes for various sensor surfaces
  • Characterization of surface properties and particle size distributions
  • Characterization of the adsorption properties of the template used

Metal-organic frameworks

© Photo Fraunhofer ICT
© Photo Fraunhofer ICT
© Photo Fraunhofer ICT

Metal-organic frameworks (MOFs) form a new class of microporous materials that are characterized by extremely large specific pore volumes (up to 3.60 cm3/g) and large specific surfaces (> 7000 m2/g) that substantially exceed those of established porous materials like silicates or activated carbon.

Structure

MOFs are composed of metallic clusters such as Zn, Cu, Fe and Zr, connected by organic linkers (e. g. terephthalate, imidazolate). They offer an infinite array of compositional possibilities, generating a wide variety of MOF substances with very different properties. MOF materials can therefore be used in very different areas of application, in particular gas storage, separation techniques, sensor development, drug delivery, environmental restoration and catalysis.

Synthesis and scale-up

Fraunhofer ICT carries out applied and industry-oriented research in the area of metal-organic frameworks. Emphasis is placed on economical synthesis routes for MOF compounds and their scale-up to the kilogram range, which forms the basis for future product developments. Synthesis protocols originally obtained through fundamental research are further optimized on the basis of reaction engineering concepts. The major goal is to simplify the synthesis processes and significantly reduce their costs. Here, questions pertaining to the economical use of resources and energy, waste reduction, product quality, space/time yield, safety and future up-scaling play an important role.

Fraunhofer ICT uses screening procedures that are conducted either continuously or batch-wise in parallel reactor set-ups, in order to identify promising synthesis routes at a very early stage during the exploration of new MOF materials. Modern analytical methods are available for characterizing the synthesis products, in particular the structure, specific surface, adsorption behavior and chemical and thermal stability of the porous materials.

MOF applications

The main research priorities at Fraunhofer ICT are currently product developments in the areas of reactive gas storage, selective sensing of hazardous substances and liquid-phase catalysis using MOFs. Starting with MOF substances known from literature we develop strategies to optimize functionality, for instance by modifying linker molecules or by post-functionalization of the entire MOF compound. As part of a strategic partnership with five other Fraunhofer institutes (Fraunhofer IWS, IKTS, IGB, ISE, and UMSICHT), further MOF applications in the areas of gas storage, heat storage, gas separation and sensor technology are explored. In addition, processes for the shaping and manufacturing of MOF semi-finished products as well as new characterization techniques are currently being developed.

Our offer

  • We provide our customers and project partners with rapid and comprehensive access to the diverse applications of metal-organic frameworks.
  • We offer a broad range of R&D services ranging from feasibility studies and expertise to product and process developments.
  • We develop, analyze and optimize MOF syntheses and MOF processes for customer-specific tasks in all areas from the laboratory to production scale.

EU/BMBF Project: SENSIndoor: Nanotechnology-based intelligent multi-SENsor System with selective pre-concentration for Indoor air quality control

SENSIndoor aims to develop novel, nanotechnology-based intelligent sensor systems for the selective monitoring of volatile organic compounds (VOCs) for demand-controlled ventilation in indoor environments. Significantly reduced energy consumption without the adverse health effects linked to sick building syndrome requires optimized ventilation concepts adapted to specific application scenarios like offices, hospitals, schools, nurseries or private homes. These must be based on selective detection and the reliable quantification of relevant VOCs such as formaldehyde or benzene at ppb or even sub-ppb levels in complex environments. The project addresses two sensor technologies with MEMS-based metal oxide semiconductor gas sensors and SiC-based gas-sensitive field effect transistors. Gas-sensitive layers for both sensor technologies are achieved using pulsed laser deposition for well-defined, stable and highly-sensitive nanostructured layers. These are combined with gas pre-concentration to boost the sensitivity of the overall system. Dynamic operation of the gas sensor elements by temperature cycling, combined with pattern recognition techniques, is employed to further boost sensitivity and selectivity, and is expanded to make optimal use of the gas pre-concentration. The project thus combines physical and chemical nanotechnologies for extremely sensitive and selective gas sensing, MEMS technologies for low-power operation as well as low-cost manufacture and finally dynamic operating modes together with advanced signal processing for unrivalled system performance. Sensor elements and systems are evaluated under controlled lab conditions derived from priority application scenarios. The final demonstration of the SENSIndoor technology will include field tests with sensor systems integrated into building control systems. The project is funded by the European Community’s Seventh Framework Programme under grant agreement no. 604311.

Fraunhofer MAVO "MOF2market", Metal-Organic Frameworks: Technology and market development for a new class of highly porous materials

In this project, novel MOF-based applications have been developed in the solar technology, membrane technology, sensor, diagnostics, gas storage and chemical processing sectors. Due to the unique properties of MOFs, these have new or improved performance parameters, making them suitable for a wide range of markets. At Fraunhofer ICT production processes and strategies are optimized in terms of reaction and process engineering and also economic factors, for integration in an industrial environment. The aim is a flexible provision of MOF substances on a technical scale. In addition, MOF-based storage systems are developed for highly reactive gases and liquids.  This cooperation between six Fraunhofer institutes ran from March 2012 to February 2015.