www.afm-journal.de FULL PAPER © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 www.MaterialsViews.com wileyonlinelibrary.com Martin E. Silvestre, Matthias Franzreb, Peter G. Weidler, Osama Shekhah, and Christof Wöll* 1. Introduction Metal-organic frameworks (MOFs) are highly ordered porous materials which have attracted a great interest due to their tun- able pore structures and chemical functionalities. [1] This novel class of hybrid materials has been used for the storage [2] and separation [3] of gases, in catalysis, [4] sensor technology [5] and drug delivery. [6] MOFs consist of organic ligands and metal or metal-oxo nodes and are formed using solvothermal proc- esses at elevated temperatures. For a number of applications, homogeneous dense and pinhole free coatings are required, for example, with regard to membranes, sensors or for elec- trochemical applications. Since the typical powder materials resulting from the conventional solvothermal synthesis process are not well suited for fabricating high-quality coatings, recently, a liquid phase epitaxy (LPE) process has been introduced to the field of MOFs by Shekhah et al. [7] Using an appropriately func- tionalized organic surface as a (two-dimensional) nucleation template and adding in a step-by-step fashion the organic ligand and the metal precursor yields crystalline, oriented and homo- geneous films of HKUST-1 with exceptionally high quality. The LPE process is not restricted to planar substrates but can, in principle, be applied to any solid particle. This will be demonstrated in the present paper by coating magnetic nanoparticles with surface-attached metal-organic framework multilayers (SURMOFs). MOF coated nanoparticles are particularly interesting for a large variety of applications, e.g., catalytic or chromatographic applications as well as tumor therapies. [8] When nanoparticles are used for catalytic or sorptive applications, the suspended nanoparticles normally have to be separated from the suspension by centrifugation or filtration in order to Magnetic Cores with Porous Coatings: Growth of Metal-Organic Frameworks on Particles Using Liquid Phase Epitaxy A novel method for the homogeneous coating of magnetic nanoparticles with metal organic frameworks (MOFs) is reported. Using a liquid phase epitaxy process, a well-defined number of [Cu 3 (btc) 2 ]nH 2 O, HKUST-1, layers are grown on COOH terminated silica magnetic beads. The structure and porosity of the deposited MOF coatings are studied using X-ray diffraction and BET analysis. In addition, size and shape of the fabricated composites are analyzed by transmission electron microscopy. Potential applications of par- ticle based MOF films include catalytic coatings and chromatographic media. DOI: 10.1002/adfm.201202078 Dr. M. E. Silvestre, Prof. M. Franzreb, Dr. P. G. Weidler, Dr. O. Shekhah, Prof. C. Wöll Institute of Functional Interfaces Karlsruhe Institute of Technology Herrman-von-Helmholtz-Platz 1, 76344 Karlsruhe, Germany E-mail: christof.woell@kit.edu Figure 1. XRD data for: a) HKUST-1 grown on COOH terminated mag- netic nanoparticles and b) HKUST-1 bulk; ∗ denotes the Fe 3 O 4 (111) Bragg-peak (Cu K α1,2). Adv. Funct. Mater. 2012, DOI: 10.1002/adfm.201202078