Functionality preservation with enhanced mechanical integrity in the nanocomposites of the metal–organic framework, ZIF-8, with BN nanosheets

Metal–organic frameworks (MOFs) are an important class of materials with potential applications in gas storage and catalysis. One of the key challenges for their practical applications is low mechanical robustness and stability as they contain signicant structural porosity and are typically fragile in nature. One possible way of overcoming this drawback is through compositing with a two-dimensional nanomaterial such as BN which has high mechanical strength. Such an effort to improve the mechanical properties of MOFs has not been reported hitherto. We have investigated, for the rst time, the possibility of enhancing the mechanical properties of a MOF, in the case of microporous zeolitic imidazolate framework ZIF-8. For this purpose, we prepared composites where ZIF-8 is chemically bonded to few-layer BN. Incorporating the properties of both BN and the MOF, especially to improve the mechanical strength of the latter, is indeed novel. Metal–organic frameworks (MOFs) and boron nitride both possess novel properties, the former associated with microporosity and the latter with good mechanical properties. We have synthesized composites of the imidazolate based MOF, ZIF-8, and few-layer BN in order to see whether we can incorporate the properties of both these materials in the composites. The composites so prepared between BN nanosheets and ZIF-8 have compositions ZIF–1BN, ZIF–2BN, ZIF–3BN and ZIF–4BN. The composites have been characterized by PXRD, TGA, XPS, electron microscopy, IR, Raman and solid state NMR spectroscopy. The composites possess good surface areas, the actual value decreasing only slightly with the increase in the BN content. The CO2 uptake remains nearly the same in the composites as in the parent ZIF-8. More importantly, the addition of BN markedly improves the mechanical properties of ZIF-8, a feature that ismuch desired inMOFs. Observation ofmicroporous features alongwith improvedmechanical properties in a MOF is indeed noteworthy. Such manipulation of properties can be profitably exploited in practical applications.