Homogeneous films with tailored microporous structures are crucial for several applications; however, fabricating such films presents significant challenges. This is primarily because most microporous materials have crystal sizes in the nano- and micrometer ranges, which inevitably generates intergranular spaces in the films, thereby complicating the fabrication of these thin films. In this study, functionalized metal–organic polyhedra (MOPs) are used as discrete microporous units and assembled into homogenous microporous films. The generation of intergranular spaces is avoided while controlling packing parameters and film thicknesses. Initially, the MOP units, influenced by van der Waals forces between carbon chains of functionalized adipic acids, display an affinity to form spindle-shaped blocks and islands. As the MOP concentration increases, these structures self-assembled into a hexagonally packed structure with an in-plane orientation and a maximum stacking of two layers of MOPs. By contrast, un-functionalized MOPs form a disordered film structure owing to random agglomeration. Evidently, functionalized adipic acid influences the orientation of the MOP network films with uniformly distributed micropores, effectively preventing the formation of intergranular spaces. Additionally, formaldehyde adsorption and desorption experiments revealed that the MOP network films possess superior adsorption and desorption capacities. The proposed approach signifies a breakthrough in the fabrication of homogenous microporous films.

The challenge for single-atom catalysts in various C-C cross coupling reaction exists in the development of solid supporting materials. It has been desired to find a supporting material designed in molecular level to anchor a single-atom catalyst and provide high degree of dispersion and substrate access in aqueous media. Here, we prepared discrete cages of metal-organic polyhedra anchoring single Pd atom (MOP-BPY(Pd)) and successfully performed a Suzuki-Miyaura cross coupling reaction with various substrates in aqueous media. It was revealed that each tetrahedral cage of MOP-BPY(Pd) has 4.5 Pd atoms on average and retained its high degree of dispersion up to 3 months in water. The coupling efficiencies of the Suzuki-Miyaura cross coupling reaction exhibited more than 90.0% for various substrates we have tested in the aqueous media, which is superior to those of the molecular Pd complex and metal-organic framework (MOF) anchoring Pd atoms. Moreover, MOP-BPY(Pd) was successfully recovered and recycled without performance degradation.