Regulation Of Mechanism For Marine MOFs Hydrogen Storage Composites Based On Spillover And Nano-confinement Of Aluminum

Solid-state hydrogen storage technology utilizing metal-organic frameworks（MOFs）has gained significant attention due to its structural and storage benefits in marine vessels.However,the physical adsorption of hydrogen on MOFs has higher storage capacities at lower temperatures,while most MOFs suffer from poor structural stability.In order to develop composite multi-metal-organic frameworks（MOFs）for hydrogen storage that balance structural stability and high-temperature hydrogen storage performance,a high-throughput screening approach combining grand canonical Monte Carlo（GCMC）simulation and machine learning（ML）algorithms was employed to establish a predictive model for the adsorption equilibrium of MOF-based hydrogen storage systems.This model was used to screen high-performance multi-composite MOF matrices.To improve the hydrogen storage capacities of MOFs at higher temperatures,the optimal adsorption configuration was determined based on the stability of the composite material configuration,the binding energy between hydrogen and the matrix,and the variation of the configuration.The MOFs material was then prepared,and its performance was tested,along with Density Functional Theory（DFT）calculations to analyze the effect of the incorporation of carbon based materials,distribution of the transitional metal on the adsorption performance of hydrogen,the effect of aluminum hydride nano-confinement on the law of the action energy.It also addresses the enhanced heat transfer problem of the hydrogen storage system faced by the composite hydrogen storage materials of multifaceted MOFs for marine applications.Researches carried out can be summarized as follows:High throughput screening of high performance hydrogen storage adsorbents for MOFs.In order to efficiently screen composite multivariate MOFs matrix materials,a multi-physics model for hydrogen storage in MOFs with temperature and pressure swings consisting of density（Density）,Henry’s law constant（H_p）,pore-limited diameter（PLD）,largest cavity diameter（LCD）,accessible specific surface area（ASA）,porosity（φ）and open metal sites（OMS）was developed using high-throughput screening,GCMC calculations and machine learning.The databases of MOFs for hydrogen storage was expanded and the key factors affecting the hydrogen storage capacity of MOFs were quantified and analyzed.It was found that the relative error between the modeled predicted hydrogen adsorption capacity of MOFs at-196°C and 3.5 MPa and the hydrogen adsorption test results was 1.01%.In the low pressure region（0.0001 MPa-0.1 MPa）,the pore structure of MOFs was the main factor affecting their hydrogen adsorption capacity,and at the higher pressure region（3.5 MPa）,the hydrogen adsorption capacity on MOFs was mainly influenced by their specific surface area.Among them,according to the established databases of hydrogen storage in MOFs,the optimal range of hydrogen storage pore structure was found to be:6（?）<LCD<12（?）,4（?）<PLD<8（?）,0.55<φ<0.70;Henry’s law constant was located in the range:5.0E-07-7.5E-07 mmol·Pa^-1·g^-1;the optimal range of Density:0.5 cm³·g^-1-1.5 cm³·g^-1;OMS optimal range:Al,Zn,Co and Cu as metal open sites.As a result,HKUST-1 was selected as the composite multifunctional hydrogen storage matrix material for MOFs.Preparation of transition metal@carbon matrix material@HKUST-1 composite.Based on the DFT calculations,the structure of the carbon matrix material and the amount of incorporation and the distribution of transition metal influenced the binding energy between hydrogen and HKUST-1 composite,and the material was prepared,structurally characterized and performance tested in the configuration with the lowest binding energy.The results showed that the most stable conformation between hydrogen and the composite matrix was obtained when AX-21,a carbon-based material with a similar pore size to HKUST-1,was selected,and the best addition mass ratio of the carbon-based material for incorporating HKUST-1 was 4.68 wt%.The best loading ratio was 1.68 wt%and the best adsorption location for the transition metal Ni was at the bottom of the MOFs framework.Compared with the original HKUST-1,the BET specific surface area,pore volume and pore diameter of the composite adsorbent specimens increased by 4.21%,1.67%and5.88%,respectively,and the thermal decomposition temperature increased by 6.66%and the heat of adsorption increased by 2.74%,respectively,and the hydrogen adsorption capacity increased by 1.26 at 25°C and 3.5 MPa.The structural properties of MOFs composites can be improved,and the induced hydrogen spillover effect can increase their hydrogen storage capacity at room temperature.Effect of nano-confinement on reversible hydrogen storage in aluminum hydride.Density functional theory（DFT）calculations were performed to determine the optimal configuration with the lowest composite binding energy for a multi-metal-organic frameworks（MOFs）composite material with Al H₃.Al H₃ was dissolved in tetrahydrofuran and impregnated into the MOFs framework using a solution-based method to create a multi-component MOFs composite hydrogen storage system with nanoscale confinement.The material preparation,structural characterization,and hydrogen storage kinetics of the Al-02 composite（Al H₃ nano-confined in carbon-based materials@MOFs@transition metals）were investigated.The results showed that the optimal composite mass ratio between Ni@H-A（transition metal loadeded on carbon-based material@MOFs）andα-Al H₃ was 10.05 wt%.Compared with Ni@H-A,the hydrogen adsorption capacity of the Al-02 sample under mild conditions dominated by physical adsorption（25°C,0.1MPa）increases by 0.5%,and the adsorption heat increases by 0.53%.The synergistic effect between hydrogen spillover and nano-confinement enhances the hydrogen storage performance of the multi-MOFs composite material.Under high-temperature and high-pressure conditions dominated by chemical adsorption（150°C,7 MPa）,compared withα-Al H₃,the Al-02 sample exhibits a decrease in hydrogen release temperature and peak temperature by 5°C and 15°C,respectively,a 15 KJ·mol^-1 reduction in activation energy,and an extension of 25.33%and 18.18%in hydrogen adsorption and desorption kinetics time,respectively.The material releases 0.85 wt%reversible hydrogen within the hydrogen adsorption/desorption cycle,and nanoscale confinement improves the hydrogen desorption kinetics of the material,achieving reversible hydrogen storage.Enhanced heat transfer in adsorption beds of composite hydrogen storage materials for marine MOFs.Based on a 7.5 k W ship hydrogen fuel cell electric propulsion test system,and according to the power system output power corresponding to the hydrogen flow rate of 20 L·min-1 under steady-state cruising conditions of a solar-powered sightseeing boat,a hydrogen storage vessel with a capacity of 0.5 liters was designed based on the principle of being adaptable for 5 minutes.Hydrogen charging and discharging tests were conducted at room temperature,a preset pressure of 3.5 MPa and 150°C,and a preset pressure of 7 MPa.Based on the approximate equivalent thermal conductivity,the tank was filled with Al-02,Eng@Al-02（5 wt%expanded graphite and Al-02 composite）,and Al-02+honeycomb thermal fins,respectively.The effects of adding ENG and equipping honeycomb fins on reducing the heat effect of the tank during hydrogen charging and discharging were compared.The results showed that when 2.5 wt%,5 wt%,and 7.5 wt%of ENG were added,the equivalent thermal conductivity of the composite sample increased by 6.25%,43.75%,and 62.50%,respectively.Under the conditions of charging and discharging hydrogen at room temperature and 3.5 MPa,compared with the Al-02-filled sample of the adsorption bed,the adsorption bed filled with Al-02+honeycomb fins and Eng@Al-02 had an average temperature reduction of 35.14%and 44.81%,respectively.The amount of cumulative hydrogen charging increased by 4.05%and decreased by 3.74%,the usable capacity ratio（UCR）decreased by 4.58%and increased by 2.67%,respectively,and the desorption rate（DR）increased by 0.69%and 2.58%.During the charging and discharging hydrogen tests at 150°C and a preset pressure of 7 MPa,all three adsorption beds reversibly released some hydrogen,with amount of cumulative hydrogen charging 4.82 g,4.74 g,and 4.84 g.Compared with the amount of cumulative hydrogen charging in the room temperature charging and discharging test,the amount of cumulative hydrogen charging increased by 50.16%,53.90%,and 45.34%,respectively.The average temperature of the adsorption bed decreased by 18.36%,6.28%,and 2.01%,respectively,UCR increased by 11.69%,18.00%,and 11.15%,respectively,and DR increased by 4.39%,3.69%,and 2.34%,respectively.The tank is equipped with honeycomb heat transfer fins more applicable to the enhanced heat transfer measures for the working conditions of the ship’s power system characteristics.