Processing of thermally stable 3D hierarchical ZIF-8@ZnO structures and their CO2 adsorption studies

Core-shell hybrid structures of ZnO-Zeolitic Imidazolate Framework-8 (ZIF@ZnO) were obtained by the solvothermal treatment of ZnO hierarchical structures having an average cluster size of ~3 µm and surface area of ~19 m2/g. The surface area and pore volume of these supported structures could be tailored as a function of reaction time and temperature. Solvothermal treatment of ZnO structures in the presence of imidazole at 95 °C for 24 h induced extremely large surface area of 733 m2/g for the ZIF@ZnO samples. Samples thus obtained demonstrated a CO2 adsorption capacity of 0.34 mmol/g at 25 °C compared to the value of 0.052 mmol/g measured for the ZnO structures. More significantly, the ZnO core helped the ZIF-8 surface fractal assemblies to significantly improve the thermal stability and retain their near spherical shapes allowing better handling in any practical adsorption application. The results validate that surface conversion of ZnO microstructures to ZIF-8 could be an efficient pathway towards the development of ZIF based supported adsorbents for CO2 separation. © 2016 Elsevier Ltd. All rights reserved

Scalable continuous production of high quality HKUST-1 via conventional and microwave heating

Metal Organic Frameworks (MOFs) are materials with large surface areas and internal volumes, which result in a number of useful properties for applications such as catalysis, separations and gas storage. However, MOFs are challenging to produce at a large scale creating a barrier to becoming truly viable alternatives to current technologies. As a first step towards industrial scale manufacture, we demonstrate here the first scalable, continuous synthesis of high-quality HKUST-1 using ethanol as the solvent, resulting in a greener and potentially much more economical process (as solvent does not decompose and thus can be recycled). We also show that microwave heating can be used to produce HKUST-1 continuously, in timescales several orders of magnitude faster than by conventional heating. We demonstrate a novel approach to microwave assisted synthesis of HKUST-1, based on a recycle loop with microwave irradiation, which is scalable under both batch and continuous conditions and allows an independent control of microwave irradiation regime and the overall reaction time. The use of microwave heating for continuous production of HKUST-1 enabled STY of 400,000 kg m−3 d−1, which is higher than any production rates reported to date, even when using the preferred high yield solvent, DMF, and is 17 times more than the highest production rates reported to date for HKUST-1 in ‘ethanol-only’ systems

Hydrolytically Stable MOF in 3D-Printed Structures

Metal–organic frameworks (MOFs) are a well‐developed field of materials, having a high potential for various applications such as gas storage, water purification, and catalysis. Despite the continuous discoveries of new MOFs, so far there are only a limited number of industrial applications, partially due to their low chemical stability and limited mechanical properties, as well as difficulties in integration within functional devices, Herein, a new approach is presented toward the fabrication of MOF‐based devices, utilizing direct 3D printing. By this method, 3D, flexible, and hydrolytically stable MOF‐embedded polymeric structures are fabricated. It is found that the adsorption capacity of the 3D‐printed MOF is retained, with significantly improved hydrolytic stability of the printed MOFs (copper benzene‐1,3,5‐tricarboxylate) compared to the MOF only. It is expected that applying 3D printing technologies, for the fabrication of functional MOF objects such as filters and matrices for columns and flow reactors, will open the way for utilization of this important class of materials.National Research Foundation (NRF