1D axial heterostructure of hydrogen-bonded framework and metal-organic framework by metalation reaction

Creating one-dimensional (1D) axial heterostructures of crystals formed from hydrogen-bonded organic frameworks (HOFs) and metal-organic frameworks (MOFs) is challenging due to their distinct chemical bonds to construct each porous architecture. In this study, we applied the metalation process, exchanging H⁺ with monovalent metal cations, to fabricate bulk crystal 1D axial heterostructures of HOF and MOF. Rod-shaped single crystals of HOFs with [N-H···N] hydrogen bonds were immersed in a Cu⁺ solution to induce metalation, resulting in MOF | HOF | MOF crystals exhibiting a 1D axial heterostructure. X-ray diffraction, scanning electron microscopy, gas sorption, and emission microscopy demonstrated that metalation began at both ends of the rod-shaped HOF crystals and took 48 hours to transform into MOF. The spatially and temporally controlled metalation facilitated the regulation of the sizes of HOF and MOF domains in the 1D axial heterostructure. The MOF | HOF | MOF crystals exhibited interface-controlled gas diffusion and various spatially-resolved photoluminescence behaviors depending on the distribution of each component.