nanomaterials Article Thin Films of Metal-Organic Framework Interfaces Obtained by Laser Evaporation Olivia L. Rose 1 , Anca Bonciu 2,3,4 , Valentina Marascu 2,5 , Andreea Matei 2 , Qian Liu 1 , Laurentiu Rusen 2 , Valentina Dinca 2,4, * and Cerasela Zoica Dinu 1, *   Citation: Rose, O.L.; Bonciu, A.; Marascu, V.; Matei, A.; Liu, Q.; Rusen, L.; Dinca, V.; Dinu, C.Z. Thin Films of Metal-Organic Framework Interfaces Obtained by Laser Evaporation. Nanomaterials 2021, 11, 1367. https:// doi.org/10.3390/nano11061367 Academic Editors: Carlos Martí-Gastaldo, Stefano Agnoli and Jorge Pasán Received: 18 March 2021 Accepted: 19 May 2021 Published: 21 May 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Chemical and Biomedical Engineering, West Virginia University, Morgantown, WV 26506, USA; olrose@mix.wvu.edu (O.L.R.); ql0009@mix.wvu.edu (Q.L.) 2 National Institute for Laser, Plasma and Radiation Physics, RO-077125 Magurele, Romania; anca.bonciu@inflpr.ro (A.B.); valentina.marascu@inflpr.ro (V.M.); andreea.matei@inflpr.ro (A.M.); laurentiu.rusen@inflpr.ro (L.R.) 3 Faculty of Physics, University of Bucharest, RO-077125 Magurele, Romania 4 IN2—FOTOPLASMAT Center, RO-077125 Magurele, Romania 5 Université Paris-Saclay, CEA, INRAE, DMTS, SCBM, F-91191 Gif-sur-Yvette, France * Correspondence: valentina.dinca@inflpr.ro (V.D.); cerasela-zoica.dinu@mail.wvu.edu (C.Z.D.); Tel.: +40-214-574-414 (V.D.); +1-304-293-9338 (C.Z.D.) Abstract: Properties such as large surface area, high pore volume, high chemical and thermal stability, and structural flexibility render zeolitic imidazolate frameworks (ZIFs) well-suited materials for gas separation, chemical sensors, and optical and electrical devices. For such applications, film processing is a prerequisite. Herein, matrix-assisted pulsed laser evaporation (MAPLE) was successfully used as a single-step deposition process to fabricate ZIF-8 films. By correlating laser fluency and controlling the specific transfer of lab-synthesized ZIF-8, films with user-controlled physical and chemical properties were obtained. Films’ characteristics were evaluated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The analysis showed that frameworks of ZIF-8 can be deposited successfully and controllably to yield polycrystalline films. The deposited films maintained the integrity of the individual ZIF-8 framework, while undergoing minor crystalline and surface chemistry changes. No significant changes in particle size were observed. Our study demonstrated control over both the MAPLE deposition conditions and the outcome, as well as the suitability of the listed deposition method to create composite architectures that could potentially be used in applications ranging from selective membranes to gas sensors. Keywords: metal-organic frameworks; MOFs; matrix-assisted pulsed laser evaporation; MAPLE; deposited films 1. Introduction Thin films of metal-organic frameworks (MOFs), coordinated combinations of metal ions and organic linkers [1,2], have been proposed for the next generation of user-designed flexible platforms of nanometer porosity to be implemented in a variety of applications ranging from sensors [3,4] to drug delivery [5], and from systems with antimicrobial [6,7] and antibacterial activities [8,9] to selective membranes for gas sensor applications [10,11]. The plethora of MOF applications are supported by the individual particle characteristics, such as high surface area, high pore volume, biocompatibility, and small size [2], with such characteristics being recently controlled through different fabrication methods such as pulsed laser deposition (PLD) [12–14], atomic layer deposition (ALD) [15,16], molecu- lar layer deposition (MLD) [17,18], spin coating [19], liquid-phase epitaxy (LPE) [20,21], chemical solution deposition (CSD) [22,23], or Langmuir–Blodgett layer-by-layer (LBL) deposition [24,25], just to name a few. Studies by Fischer et al., for instance, demonstrated Nanomaterials 2021, 11, 1367. https://doi.org/10.3390/nano11061367 https://www.mdpi.com/journal/nanomaterials