RESUMEN
In situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was developed for the first time to observe the hydrogen isotope separation behavior at active CuI sites within CuI-MFU-4l, and clear evidence of the preferential adsorption of D2 over H2 was directly captured. More importantly, our results show direct spectral proof to clarify the chemical affinity quantum sieving mechanism of hydrogen isotope separation within porous adsorbents.
RESUMEN
Realizing ideal deuterium separation from isotopic mixtures remains a daunting challenge because of their almost identical sizes, shapes, and physicochemical properties. Using the quantum sieving effect in porous materials with suitable pore size and open metal sites (OMSs) enables efficient hydrogen isotope separation. Herein, synthetic HKUST-1-derived microporous mixed-valence Cu(I)Cu(II)-BTC (BTC = benzene-1,3,5-tricarboxylate), featuring a unique network of distinct Cu(I) and Cu(II) coordination sites, can remarkably boost the D2/H2 isotope separation, which has a high selectivity (SD2/H2) of 37.9 at 30 K, in comparison with HKUST-1 and other porous materials. Density functional theory (DFT) calculations indicate that the introduction of Cu(I) macrocycles in the framework decreases the pore size and further leads to relatively enhanced interaction of H2/D2 molecules on Cu(II) sites. The significantly enhanced selectivity of Cu(I)Cu(II)-BTC at 30 K can be mainly attributed to the synergistic effect of kinetic quantum sieving (KQS) and chemical affinity quantum sieving (CAQS). The results reveal that Cu(I) OMSs exhibit counterintuitive behaviors and play a crucial role in tuning quantum sieving without a complex structural design, which provides a deeper insight into quantum sieving mechanisms and a new strategy for the intelligent design of highly efficient isotope systems.
RESUMEN
Membrane gas separation offers high energy efficiency, easy operation, and reduced environmental impacts for vast hydrocarbon recovery in the petrochemical industry. However, the recovery of real light hydrocarbon mixtures (e.g., olefin/nitrogen) remains challenging for lack of high-performance membranes with sufficient reverse selectivity (large molecules permeate faster) and permeability. Here, we report the incorporation of fine-tuned, giant-pore featured MIL-101 nanocrystals into rubbery polymers to fabricate hybrid membranes, which successfully exploited the giant-pore channels and large sorption volume of the MIL-101 pore system. The synthesized MIL-101/poly(dimethylsiloxane) (PDMS) hybrid membranes demonstrated remarkably simultaneous improvement of gas permeance and separation factor for the model gas mixture propylene/nitrogen. Compared with the pristine PDMS, the propylene permeance and separation factor could be improved by more than 50% by adjusting MIL-101 loading and operating conditions. By consulting molecular simulations and gas sorption analysis, we verified that the giant-pore system of MIL-101 and the elastic PDMS chains exhibited a synergistic effect on improving both hydrocarbon solution and diffusion. Pore properties of MIL-101 contributed favorably to accelerated propylene diffusion in MIL-101 that is 236% faster than that in PDMS. In the meantime, MIL-101 reinforced the hydrocarbon solution additionally to PDMS, which further facilitated hydrocarbon transport.
RESUMEN
The catalytic mechanism of doped complex hydrides for hydrogen storage remains unconfirmed. Here, we report a simple method to separate the active species of Ti-based catalysts in NaAlH(4) by filtration using tetrahydrofuran (THF) as solvent. The results show that the average particle size of the obtained Al-Ti active species is 30-50 nm.
