Surface coating of MOF layers on the nanocrystals of other MOFs using nanoparticle mediated nucleation for the efficient removal of formaldehyde

The coating of metal-organic frameworks (MOFs) has been desired to control the surrounding environment of the substrate and the pathway for the guest molecules approaching. Especially, the MOF layer coating on the other MOF nanoparticles has been challenging because of lattice mismatch and undesired homogeneous nucleation. In this report, we coated MOF layers on other nanocrystalline MOFs (nMOFs) using metal nanoparticle mediated nucleation method, and showed how this coating can be used for unique sorption behavior of H2O and efficient removal of trace formaldehyde existing in ppm level in air. Specifically, the layers of MOF-801 and UiO-66 were grown from the N nanoparticles attached on the particles of nUiO-66 and nMOF-801 to result final products of nMOF-801 subset of UiO-66 and nUiO-66 subset of MOF-801, respectively. We found that these samples of nUiO-66 subset of MOF-801 and nMOF-801 subset of UiO-66 present unusual H2O uptake behaviors originated from the sequence of condensation between inner and outer MOFs. These samples also captured 7 times higher amount of formaldehyde than an activated carbon and had high affinity to release less amount of formaldehyde even when its concentration outside is low.