ZnO Nanorod-Induced Heteroepitaxial Growth of SOD Type Co-Based Zeolitic Imidazolate Framework Membranes for H₂ Separation

Abstract

Up to now, the fabrication of well-intergrown Co-based zeolitic imidazolate framework (ZIF) membranes on porous tubular supports is still a major challenge. We report here a heteroepitaxial growth for preparing well-intergrown Co-based ZIFs (ZIF-67 and ZIF-9) tubular membranes with high performance and excellent thermal stability by employing a thin layer of ZnO nanorods acting as both nucleation centers and anchor sites for the growth of metal-organic framework membranes. The results show that well-intergrown Co-ZIF-67 and Co-ZIF-9 membranes are successfully achieved on the ZnO nanorod-modified porous ceramic tubes. This highly active heteroepitaxial growth may be attributed to the fact that the (Zn,Co) hydroxy double salt intermediate produced in situ from ZnO nanorods acts as heteroseeds and enables the uniform growth of Co-based membranes. The H/CO selectivity of the as-prepared Co-ZIF-9 tubular membrane could reach about 23.8 and the H/CH selectivity of Co-ZIF-67 tubular membrane is as high as 45.4. Moreover, the membranes demonstrate excellent stability because of the ZnO nanorods as linkers between the membrane and substrate.

H2/CO2 separations in multicomponent metal-adeninate MOFs with multiple chemically distinct pore environments

“…52 Sorbents, MOFs and ZIFs in particular, have been explored as attractive low-cost alternatives to distillation for H 2 /CO 2 separations. [53][54][55][56][57][58][59][60][61][62][63][64] To test the H 2 /CO 2 separation capabilities of bMOF-200, we rst conducted column breakthrough experiments. A feed gas ratio of 80 : 20 H 2 : CO 2 was selected as an approximate to the relative ratios aer industrial scale water gas shi (WGS) reactions using methane as the feedstock.…”

Solvent‐free route for metal–organic framework membranes growth aiming for efficient gas separation

“…The unreacted metal precursor will exhibit no negative effect on the gas separation performance, because the gap among the nanorods or nanosheets is big enough for gas diffusion with low resistance compared to the diffusion in the MOF membrane with subnanometer‐size pore . On the contrary, the unreacted metal precursor can even enhance the structure stability of the membrane.…”

“…On the contrary, the unreacted metal precursor can even enhance the structure stability of the membrane. Several MOF membrane architectures were designed to be supported on vertically aligned metal precursors, such as Zn or ZnO, where the strut‐like structure allowed for greater vertical and lateral movements that could compensate for the mismatch in the expansion coefficients of the membrane, and the membranes demonstrated excellent stability because of the metal precursors as linkers and buffering layers between the membrane and substrate with strong adhesion …”

“…Second, it is found that the transformation extent of the ZnO nanorods is around 95.7% from the Rietveld refinement of the XRD result of the ZIF‐8 membrane (shown in Figure ). The unreacted metal precursor of ZnO nanorods serve as linkers and buffering layers between the membrane and substrate, exhibiting strong adhesion and compensating the mismatch of the expansion coefficients, which contribute to the membrane stability …”

Investigation on Stranski–Krastanow (SK) Growth Mode of Ag Coating in Cu/Ag Core-Shell Composites

“…The morphology of particles is related to the catalytic properties, so the growth mode of the coating has attracted great attention. Heteroepitaxial growth has been demonstrated in film materials, which is dependent on the lattice mismatch between the coating and the substrate [11,12]. In core-shell composites, the HRTEM images of the interface were used to investigate the deposition of the coating.…”