The hollow filler has been verified to effectively enhance the CO 2 permeability of mixed matrix membrane (MMMs) by constructing low-resistance transport pathway. However, the in-continuity of hollow fillers across the membrane results in insufficient CO 2 permeability. In this work, the micron-sized hollow ZIF-8 (Mic-H-ZIF-8) were designed and proposed to accumulate continuously across the membrane to construct the transport highway for CO 2 . Importantly, the in-situ polymerization was utilized to achieve continuous accumulation of the Mic-H-ZIF-8 fillers across the membrane. The Mic-H-ZIF-8 presents cavity size of 4 μm and shell thickness of 100 nm, and three or four Mic-H-ZIF-8 microspheres are aligned sequentially across the membrane, in which the effective gas transport distance is decreased from 13 μm to the range of 0.8–3 μm. Consequently, the CO 2 permeability of 5 wt% Mic-H-ZIF-8/PEO MMM is 224.6 % and 63.5 % higher than those of pure PEO membrane and nanosized hollow ZIF-8/PEO MMM at 0.1 MPa. Meanwhile, the CO 2 /N 2 selectivity is still as high as 70.0. This CO 2 separation performance is far exceeding the Robeson upper bound in 2008, and beyond the McKeown upper bound in 2019 as the feed pressure increasing, confirming the significance of continuous transport highway constructed by micron-sized hollow MOFs on improving CO 2 separation of MMMs.
MOFs-based yolk-shell composites are newly-presented but promising catalysts in the area of catalysis. In this work, a kind of unique rattle-type Pd/ZnO@hollow ZIF-8 yolk-shell catalyst is developed via a ZnO-template approach, in which there exist two processes of both ZnO-induced ZIF-8 formation and ZnO dissolution. Of prime importance is that ZnO was selected as the sacrificial template since it can not only be etched in the solution of ligands but also assist the formation of compact ZIF-8 shell by providing nucleation sites via linker activation. It is also proposed that sufficient amount of Zn(NO 3 ) 2 ·6H 2 O and 2-methylimidazole added in the growth solution of ZIF-8 should accelerate the outward growth of ZIF-8 layer as well as dissolution of ZnO. This way, the final construction of Pd/ZnO@hollow ZIF-8 yolk-shell materials is achieved. Compared to the Pd/ZnO counterparts, Pd/ZnO@hollow ZIF-8 rattle-type catalysts demonstrate a promoted behavior in terms of size-selectivity for the liquid hydrogenations of alkenes due to the outer ZIF-8 shell acting as a molecular sieve. It can also protect the catalytically active Pd NPs from poisoning and leaching, giving rise to an excellent stability. Moreover, the yolk-shell catalysts manifest a better activity beyond their core-shell counterparts since the presented interior hollow space between core and shell is likely to expose more active surfaces to reactants.
Yilin Wu,Yanke Xu,Faguang Ma,Jingjing Zhen,Yue Li,Fanlei Kong,Ming Yan
In this study, modified hollow e-ZIF-8 nanoparticles with a hollow structure and hydroxyl-rich surface were ingeniously synthesized through a one-step etching method, thereby increasing the contact area and addressing the issue of stacking imprinting sites, fundamentally enhancing selectivity. Among these, the hollow structure of the e-ZIF-8 nanoparticles not only increased the interlayer spacing of the graphene oxide (GO) nanosheets, providing additional pathways for water molecules, but also, through π-π interactions, cross-linked the phenol-modified nanoporous metal-organic frameworks (MOFs) with the GO nanosheets, significantly enhancing the structural stability and anti-fouling capability of the composite membrane. The effects of different e-ZIF-8 addition amounts on membrane flux and hydrophilicity were investigated, constructing a GO-based imprinting structure on the stacked e-ZIF-8/GO nanosheet surfaces, offering a novel strategy to improve the selectivity and stability of the membrane. The maximum adsorption capacity of e-MG-IMs reached 38.35 mg g −1 , demonstrating good selective separation factors ( α RBV/ACV = 3.24, α RBV/AZT = 2.41 and α RBV/LAM = 4.21), as well as excellent permeation selectivity ( β ACV/RBV = 4.75, β AZT/RBV = 4.42 and β LAM/RBV = 5.92). In this study, the optimized regulation of GO nanosheets extended the molecular transport channels, facilitating the construction of more molecular recognition sites, thus positively impacting the separation performance of the imprinting membrane.
危险品化学品经营许可证（带存储）