Hydrogen Isotope Thermodynamic Quantum Sieve Effect Study Of Microporous Metal Organic Framework Materials

Facing the global crisis of energy shortage and environmental deterioration of sustaina'bility of human society,nuclear fusion,regarding to be the ideal energy solution strategy,has been received worldwide focus.However,hydrogen isotope separation,being one of the key technological problems in realizing the exploitation and utilization of nuclear fusion energy,is far from effectively settled to date yet:isotopic molecules of hydrogen share almost identical size,shape and thermodynamic properties,thus,extracting,separating and purifying hydrogen isotopes from their isotopic mixtures is challenging and extremely difficult,which had really puzzled relevant researchers around the world for decades.Traditional methods for separation of hydrogen isotopes such as cryogenic distillation,electrolysis,proton exchange or the Girdler sulfide process,centrifugation,thermal diffusion,chromatography,metal hydride absorption/adsorption and laser isotope separation etc.all show a poor separation factor and high energy consumption,making them costly and far less economic in practical use.Therefore,it remains a stimulating and urgent task for relevant researchers to exploit new alternative efficient methods on hydrogen isotope separation and purification,among which,quantum sieving(QS)proposed by Beenakker et al.recently shows great prospect.Quantum sieving was pronounced in situations where the difference between the pore size and molecular hard core becomes comparable to the de Broglie wavelength.In this confinement,the zero-point energy of gas molecules overcompensates the interaction potential and thereby produces greater diffusion barriers for lighter isotopes.There exist two quantum sieving effects for hydrogen isotope separation:one is the equilibrium quantum sieving effect(EQS),and the other one is the kinetic quantum sieving effect(KQS).Considering a shortage of experimental research on separation of real hydrogen isotope mixtures under ultralow temperature due to a bottleneck encountered and a deficiency of neglecting the influence of temperature towards the relationship of the performance of quantum sieving versus the pore size,this time in this dissertation,we screened suitable metal-organic framework material(MOFs)and designed experiments,conducted a detailed and intensive study of hydrogen isotope separation,based on the equilibrium quantum sieving effect,main contents and results are summarized below:(1)Designed and established an advanced cryogenic thermal desorption spectroscopy (ACTDS)set-up for equilibrium quantum sieving study of real hydrogen isotopic mixtures,surmounting the limitation of ultralow temperature,and conducted equilibrium quantum sieving experiments of real hydrogen isotopic mixture,enriched the fundamental experimental data of equilibrium quantum sieving of real hydrogen isotopic mixture;(2)Designed and established a high temperature thermal desorption spectroscopy(TDS)set-up and made a quadrupole mass spectroscopy(QMS)calibrated for the quantitative analysis of hydrogen isotopes:i.TiHx/TiDx were suitable chosen to be the standards for calibration of QMS as an effective tool for quantitative analysis of hydrogen isotopes,the standard curves got from which were in good linearity;ii.The MS here used in this study was working in its linear response range of a signal of 0 to 5×10-8 Amps;iii.Deviations originated from monoatomic H+/D+ follow a tendency of decreasing as the amount of hydrogen/deuterium increases,heating rate does no influence on the calibration constant,while,smaller heating rate may cause bigger monatomic deviation;iv.Due to the mass discrimination of the ion source and the isotopic fractionation effect of the molecular pump,the actual sensitivity of MS towards H2 and D2 is not the same,revealing some deviation from theoretical;v.In real H2/D2 mixture MS detection,the inevitable generated HD is reasonable to be neglected.(3)Ultralow temperature separation of D2/H2 mixture through equilibrium quantum sieving was experimentally examined on {[Fe(OH)(H2bta)](H2O)}n(denoted as "AHEFAU")which was carefully screened through theoretical calculation,with an extreme two-dimensional confinement(X2DC)formed,an extraordinary separation factor as high as 41.4±0.4 at 20 K was firstly experimentally obtained,proving sufficiently the feasibility of quantum sieving as an effective mothed for actual hydrogen isotope separation;(4)Ultralow temperature separation of D2/H2 mixture through equilibrium quantum sieving was experimentally examined on[Cu2(pzdc)2(pyz)]n(denoted as "CPL-1")which was also carefully screened through theoretical calculation,with high attention focused on the influence of temperature towards the relationship of the performance of quantum sieving versus the pore size.Finally,a law of the optimal relationship of the pore size of equilibrium quantum sieving versus temperature was verified from our experiment:for equilibrium quantum sieving,for a certain kind of material with particular pore size,there exists an optimal temperature(range).Hereof,we also deduced a deduction from the law of the optimal relationship of the pore size of equilibrium quantum sieving versus temperature:for equilibrium quantum sieving,for a certain temperature,there exists an optimal pore size(range).Considering the principle of quantum sieving,we also predict that as for kinetic quantum sieving,a law of the optimal relationship of the pore size of kinetic quantum sieving versus temperature similar to the equilibrium one also exist.The revelation of this law will undoubtedly find its instructive function in condition optimation of the future quantum sieving as an effective mothed for actual hydrogen isotope separation.