Abstract A novel bilayer metal-organic framework (viz., MOF@MOF, based on Zr-MOFs via epitaxial growth of UiO-bpy on preformed UiO-66) assembled with two-dimensional MoOx species was designed and synthesized. The MoOx@UiO-66@MoOx@UiO-bpy… Click to show full abstract
Abstract A novel bilayer metal-organic framework (viz., MOF@MOF, based on Zr-MOFs via epitaxial growth of UiO-bpy on preformed UiO-66) assembled with two-dimensional MoOx species was designed and synthesized. The MoOx@UiO-66@MoOx@UiO-bpy composite would improve substrates/products diffusion, avoid active metals leaching, and crucially provide a new platform via trapping intermediates and regulating the desired reaction direction. As confirmed via characterization results, MoOx@UiO-66@MoOx@UiO-bpy with micro-/mesopores and strong acid sites (Lewis and Bronsted) exhibited good thermal and chemical stability. The bilayer MoOx@UiO-66@MoOx@UiO-bpy was further tested in cascade-selective biphase cyclopentene oxidation and exhibited 10.3% cyclopentene conversion and 16.9% glutaric acid selectivity higher than those of MoOx@UiO-66, due to its large specific surface area, high content of MoOx species, micro-/mesoporous structure, and bilayer catalytic effect. Its good reusability (> 10 runs) in the solvent-free-biphase cyclopentene oxidation suggested multidimensional encapsulation of active species in bilayer MOFs providing new idea for designing high-selectivity/stability heterogeneous catalysts. Besides, a set of reaction kinetic models with detailed kinetic parameters and a detailed reaction mechanism were provided, reconfirming the key to develop the technology of cyclopentene to glutaric acid was to conquer cyclopentene oxide hydrolysis activation energies (E2 and E4). Compared to our previous study, E2 and E4 values were decreased 93.8 and 31.7 kJ⋅mol−1, respectively.