Sequentially epitaxial growth multi-guest encapsulation strategy in MOF-on-MOF platform: Biogenic amine detection and systematic white light adjustment

MOF-on-MOF heterostructures possess multiple advantages inherited from various single-component metal–organic frameworks (MOFs). Here, we prepare a three-dimensional (3D) anionic fluorescence MOF {[In5(dpda)4(H2O)4]·H3O·3H2O}n (In-dpda) (H4dpda = 3-(3′,5′-dicarboxyphenyl)pyridine-2,6-dicarboxylic acid) with open 1D square channels. Due to the high lattice match (>97.8 %), classical ZIF-8 with powerful guest encapsulation ability controllably grows on the fluorescent core In-dpda to assemble a ZIF-8-on-In-dpda heterostructure through the sequentially epitaxial growth strategy. In addition, a smart ratiometric fluorescence sensor F-10c ⊂ ZIF-8-on-In-dpda is further constructed by synchronously encapsulating the fluorescein (F) during the epitaxial growth of ZIF-8 nanoparticles and presents high sensitivity to a biogenic amine with a low limit of detection of 4.7 nM at the 10 cycles assembly. The dual detection modes of both ratiometric fluorescent intensity and CIE chromaticity show a potential application in food safety monitoring. Meanwhile, multi-guest molecules F and rhodamine B are sequentially encapsulated in the guests ⊂ ZIF-8-on-In-dpda to achieve diverse luminescent colors including white light emission. This work presents a sequentially epitaxial growth strategy based on the lattice matching principle to assemble MOF-on-MOF platforms for multiple applications.