Volumetric Storage Capacity Research Articles

How a hydrogen start-up can contribute to the energy transition through the emerging hydrogen economy

How a hydrogen start-up can contribute to the energy transition through the emerging hydrogen economy

Hydrogen release from a metal hydride tank with phase change material jacket and coiled-tube heat exchanger

Hydrogen fuel cells are received increasingly wide attention in order to develop green ships and reduce greenhouse gas emissions in the field of waterway transportation. Metal hydrides (MHs) can be used to store hydrogen for green ships due to their high volumetric storage capacity and safety. Various measures should be considered in the design and manufacture process of the MH reactor to strengthen its performance of heat and mass transfer and obtain an acceptable hydrogen storage capacity. In this work, LaNi5 hydride is used as the hydrogen storage material and packed in the reactor. A basic axisymmetric numerical model for the hydrogen storage system without a heat exchanger has been developed and proved to be effective through the comparison between its simulation results and the published data during dehydriding. A hybrid heat exchanger, which is consisted of a phase change material (PCM) jacket and a coiled-tube, has been applied into the hydrogen storage system to relieve the thermal effect of MH in the dehydriding process on system performance. Effects of the heat transfer coefficient between the circulating heating water in the coil-tube and the MH bed, the temperature of circulating heating water and the pressure at the outlet on the dehydriding performance have been investigated. Based on parametric study, the relationships among the average dehydriding rate, the heat transfer coefficient, the heating water temperature and the outlet pressure have been found and fitted as simple equations. These fitted equations can be considered as a reference, which provides an important method to effectively control the dehydriding rate in order to satisfy the fuel requirement of the power unit and ensure the safe navigation of green ships in the future.

Evaluation of the energy storage performance of PCM nano-emulsion in a small tubular heat exchanger

PCM emulsions have attracted considerable interest as the media for thermal energy storage (TES) owing to their high thermal storage capacity, desirable fluidity and thermal conductivity. However, the direct transportation of PCM emulsions in TES systems for both charging and discharging is rarely reported. In this work, a PCM-in-water nano-emulsion was prepared with n-hexadecane and suitable surfactants for cooling energy storage at a charging and discharging temperature range of 20–5 °C and 5–15 °C, respectively. It was applied to a tubular heat exchanger system to evaluate its TES performance for a cooling panel of 0.2 m2 total surface area. The thermal storage performance was notably increased with the flow rate of emulsion through the exchanger tube. The volumetric thermal storage capacity of charging was 50% higher than that of water. The cooling energy could be rapidly released in the discharging process, 79% of the stored energy at averaging 25 W during most of the discharging period. The emulsion remained stable throughout the test period. Overall, the results demonstrated that the PCM nano-emulsion has the unique characteristics of high static stability, and high energy releasing efficiency and the promising potential for air-conditioning application in buildings.

Hydrogen storage capacity of Li-decorated borophene and pristine graphene slit pores: A combined ab initio and quantum-thermodynamic study

Among the two-dimensional materials of the post-graphene era, borophene has raised an enormous interest due to its unprecedented diversity of structures and the wide variety of potential applications, including its ability for hydrogen storage. In the present paper we use van der Waals-corrected density functional theory in conjunction with a quantum-thermodynamic model to investigate the hydrogen storage capacity of confining Li-decorated borophene sheets in its most stable Pmmn8 configuration. Our theoretical approach surpasses the standard density functional theory calculations only valid at zero temperature and no pressure, thus providing the gravimetric and volumetric capacities as well as the isotherms in real conditions. We show that narrow Li-decorated slit pores of borophene have a good volumetric hydrogen storage capacity particularly at low temperature. Accordingly, nanoporous boron frameworks could be optimal for hydrogen storage in applications at low temperature. We compare the results with those corresponding to pristine graphene slit pores.

Li4(OH)3Br-Based Shape Stabilized Composites for High-Temperature TES Applications: Selection of the Most Convenient Supporting Material.

Peritectic compound Li4(OH)3Br has been recently proposed as phase change material (PCM) for thermal energy storage (TES) applications at approx. 300 °C Compared to competitor PCM materials (e.g., sodium nitrate), the main assets of this compound are high volumetric latent heat storage capacity (>140 kWh/m3) and very low volume changes (<3%) during peritectic reaction and melting. The objective of the present work was to find proper supporting materials able to shape stabilize Li4(OH)3Br during the formation of the melt and after its complete melting, avoiding any leakage and thus obtaining a composite apparently always in the solid state during the charge and discharge of the TES material. Micro-nanoparticles of MgO, Fe2O3, CuO, SiO2 and Al2O3 have been considered as candidate supporting materials combined with the cold-compression route for shape-stabilized composites preparation. The work carried out allowed for the identification of the most promising composite based on MgO nanoparticles through a deep experimental analysis and characterization, including chemical compatibility tests, anti-leakage performance evaluation, structural and thermodynamic properties analysis and preliminary cycling stability study.

C7N6 monolayer as high capacity and reversible hydrogen storage media: A DFT study

Searching advanced materials with high capacity and efficient reversibility for hydrogen storage is a key issue for the development of hydrogen energy. In this work, we studied systematically the hydrogen storage properties of the pure C7N6 monolayer using density functional theory methods. Our results demonstrate that H2 molecules are spontaneously adsorbed on the C7N6 monolayer with the average adsorption energy in the range of 0.187–0.202 eV. The interactions between H2 molecules and C7N6 monolayer are of electrostatic nature. The gravimetric and volumetric hydrogen storage capacities of the C7N6 monolayer are found to be 11.1 wt% and 169 g/L, respectively. High hardness and low electrophilicity provides the stabilities of H2–C7N6 systems. The hydrogenation/dehydrogenation (desorption) temperature is predicted to be 239 K. The desorption temperatures and desorption capacity of H2 under practical conditions further reveal that the C7N6 monolayer could operate as reversible hydrogen storage media. Our results thus indicate that the C7N6 monolayer is a promising material with efficient, reversible, and high capacity for H2 storage under realistic conditions.

An experimental study of the active cooling performance of a novel radiant ceiling panel containing phase change material (PCM)

Phase change materials (PCMs) can increase a building’s thermal mass, reducing temperature fluctuations and peaks. However, without active discharge, the PCM’s heat removal capability depends on outdoor temperature fluctuations. The present experimental study investigated the operation and performance of a novel macro-encapsulated PCM panel (MEP) with embedded pipes as an active ceiling cooling component compared to commercially available radiant cooling technologies. The results show that if the PCM was fully discharged, the installed heat storage capacity was enough to shift the cooling demand to off-peak hours. The MEP’s specific cooling power during melting was between 5.3 and 27.7 W/m2, with 11.3 W/m2 on average over the active ceiling surface for a water supply temperature and flow rate of 20 °C and 140 kg/h, respectively. Under the same conditions, the MEP performance was close to that of the radiant ceiling panels, providing a thermal environment within Category II of EN16798 for 83% of the occupied time. This is significantly better than was achieved by actively cooled gypsum panels with micro-encapsulated PCM whose pipes were in contact with them but not embedded. With its high volumetric heat storage capacity, the MEP could represent a viable thermally active building component for building refurbishment.

Grand canonical Monte Carlo simulations of methane adsorption in fullerene pillared graphene nanocomposites

The objective of this study is to investigate the methane adsorption performance of fullerene pillared graphene nanocomposites (FPGNs) with adjustable micro and meso porous morphology and high surface/weight ratios. Different types of fullerenes are considered as pillar units to adjust the porosity of FPGNs. The gravimetric, volumetric and deliverable methane storage capacities of FPGNs are examined using grand canonical Monte Carlo (GCMC) simulations. The lithium doping strategy is also employed to further improve the methane adsorption performance of FPGNs. GCMC simulations revealed that FPGNs have promising potential for methane storage applications with the appropriate selection of design parameters. In particular, the simulation results demonstrated that the gravimetric absolute methane uptake of FPGNs could reach 12.5 mmol/g at 298 K and 40 bars and, this value could be increased up to 19.7 mmol/g with appropriate doping ratio under the same conditions.

Recent advancement in consolidation of MOFs as absorbents for hydrogen storage

Metal-organic frameworks (MOF) have emerged as a promising material for green engineering applications due to their attractive properties. But the successful implementation of this material in the field of fuel cell technologies is still a challenge. Researchers have reported more than 50% reduction in experimental bulk density of compacted MOFs relatively to their theoretical crystal density. This has resulted in reduction of gravimetric and volumetric H2 storage capacities of MOFs. Significant experimental research should be directed toward the consolidation of MOFs to meet (6.5 wt%; 50 g/L) 2025 DoE target for onboard H2 storage systems. We present an overview of green engineering materials for hydrogen storage systems. The review also summarizes recent advancement in the consolidation of MOFs as absorbents for hydrogen storage. The influence of densification techniques on MOFs textural properties, mechanical stability were discussed. Hydrogen storage capacity of both powder and densified high-performance MOFs were presented.

Medium-temperature thermochemical energy storage with transition metal ammoniates – A systematic material comparison

Materials with high volumetric energy storage capacities are targeted for high-performance thermochemical energy storage systems. The reaction of transition metal salts with ammonia, forming reversibly the corresponding ammonia-coordination compounds, is still an under-investigated area for energy storage purposes, although, from a theoretical perspective this should be a good fit for application in medium-temperature storage solutions between 25 °C and 350 °C.In the present study, the potential of reversible ammoniation of a series of transition metal chlorides and sulphates with gaseous ammonia for suitability as thermochemical energy storage system was investigated. Among the investigated metal chlorides and sulphates, candidates combining high energy storage densities and cycle stabilities were found. For metal chlorides, during the charging / discharging cycles in the presence of ammonia slow degradation and evaporation of the materials was observed. This issue was circumvented by reducing the operating temperature and cycling between different degrees of ammoniation, e.g. in the case of NiCl2 by cycling between [Ni(NH3)2]Cl2 and [Ni(NH3)6]Cl2. In contrast, sulphates are perfectly stable under all investigated conditions. The combination of CuSO4 and NH3 provided the most promising result directing towards applicability, as the high energy storage density of 6.38 GJ m−3 is combined with full reversibility of the storage reaction and no material degradation over cycling. The results of this comparative systematic material evaluation encourage for a future consideration of the so far underrepresented transition metal ammoniates as versatile thermochemical energy storage materials.

(Invited) Faradaic Charge Storage and Supercapattery Explained

Merit-merge of rechargeable batteries with supercapacitors is desirable because the two have complementary charge storage properties, namely larger storage capacity in the former, but higher power capability, greater efficiency and longer durability in the latter. It can be easily achieved via external connections, but this approach sacrifices both volumetric and gravimetric storage capacity. The more space-material efficient approach is internal combination, which can be achieved either at the material or device level [1]. In 2007, two new hybrids were proposed, namely lithium-ion capacitor [2] and supercapattery [3]. Whilst both terms describe internal hybridization, lithium-ion capacitor exemplifies at the device level, but supercapattery encompasses both material and device combinations. Because of its similarities to lithium-ion battery, lithium-ion capacitor has attracted fast growing R&D interest and investment, followed by various other ion capacitors [4]. Attention to supercapattery has grown only in the past few years, largely because the ion capacitor concept is not applicable to many new materials that are capable of Faradaic charge storage, but not specific for a particular ion. Another reason for the increased attention to supercapattery is related to the concept of pseudocapacitance which has long been identified to result from Faradaic charge storage. However, there are two Faradic storage mechanisms, namely Nernstian storage and capacitive storage, which were not acknowledged by many, leading to confusions and misleading claims in the literature. The past five years have seen much improved understanding of these issues, which will be summarized and selectively analyzed in this presentation, in relation with supercapattery. An example is to experimentally differentiate between electric double layer capacitance and pseudocapacitance by electron spin resonance (ESR) spectroscopy [5,6], as shown in Figure 1.

Reaction Mechanism Exploration of Binary Oxide Bi2Mo3O12@Ti3C2 Composite As Anode for Li-Ion Capacitor

Metal oxides as pseudocapacitive materials are widely explored as anode for lithium ion capacitors, owing to their high volumetric and gravimetric lithium storage capacities. We present studies on reaction mechanism of binary Bi2Mo3O12 oxide as an anode for lithium storage. In-situ synchrotron XRD measurements are performed on this exotic material to elucidate lithium storage behaviors, coupled with voltage resolved CVs and ex-situ XPS analyses. Synergistic effect is believed to be the factor on improving electrochemical performance of the binary metal oxide anode instead of simple combination of two single components. The Bi2Mo3O12 anode undergoes an initial irreversible conversion reaction resulting in metallic Bi and Li2MoO4 on electrochemical discharge down to 0.01 V vs. Li+/Li. During successive cycling, the two components reversibly uptake and release lithium ions through alloying/de-alloying and intercalation/de-intercalation reactions by forming Li3Bi alloy and Li2+xMoO4. Cycling stability of the Bi2Mo3O12 anode is considerably enhanced by in-situ composition of Ti3C2 MXene. The Bi2Mo3O12@Ti3C2 composite anode exhibits 227 mAh/g capacity upon prolonged 1000 cycles at 2.5 A/g high charge/discharge rate in the voltage range of 3.0 - 0.01 V. This performance indicates the Bi2Mo3O12@Ti3C2 composite can be a potential candidate as anode for Li-ion capacitors.

Cation Intercalation Materials and Cell Design for Low-Energy Electrochemical Desalination

Due to the growing population and human-made climate change spurred by the use of fossil fuels, the urgent need for energy-efficient desalination has motivated research into electrochemical desalination as a technology to remove salt ions from water. Prussian Blue analogues (PBAs) are a promising class of redox-active intercalation compounds with high capacity and cycle life used in sodium-ion batteries. While their functionality was previously shown to enable desalination in symmetric cation intercalation desalination (CID) cell architectures [S. Porada, A. Shrivastava, P. Bukowska, P. M. Biesheuvel, and K. C. Smith, Electrochim. Acta 255, 369 (2017)], they have low electronic conductivity which limits their charge and discharge rates while causing high energy consumption due to ohmic losses [A. Shrivastava and K. C. Smith, J. Electrochem. Soc. 165, A1777 (2018)]. A common technique to increase electronic conductivity in battery electrodes is the inclusion of additives such as carbon black, however increasing conductive particle content reduces active particle loading and overall salt absorption capacity. To overcome these limitations, the effects of volume fraction of either C45 or Ketjen Black conductive additive on electrode transport properties were studied, and we demonstrated that orders of magnitude improvement in electronic conductivity could be achieved using the smaller Ketjen Black particles [E. R. Reale, A. Shrivastava, and K. C. Smith, Water Res. 165, 114995 (2019)]. Through this discovery, the low electronic conductivity of PBA electrodes was overcome, and new higher-conductivity electrodes were successfully fabricated and used in a flow-through cation intercalation desalination cell built with a custom-designed 3D printed flow field. The new CID cell functioned using a PBA anode and cathode separated by an anion exchange membrane to transport salt into one half of the cell while desalinating the other, and displayed energy consumption an order of magnitude lower than that of other electrochemical desalination technologies while removing similar quantities of salt from an influent feed. For a salt concentration of 100 mM, a salinity comparable to brackish water found in areas such as estuaries and aquifers, approximately 25% of influent salt was removed from one feed and transferred into the other. Further improvements can be made through the use of intercalation materials with higher volumetric storage capacity and increased mobility for sodium, which were both limiting factors when using PBAs which lowered utilization and prevented higher salt removal. Early tests with such electrodes have shown their electronic conductivity to be several times higher than PBA electrodes, further reducing energy consumption. Another modification to the cell is the use of an in-house designed recirculation system to increase salt removal over multiple passes rather than single-pass flow. The goal of our research is to develop CID technology into a form of energy-efficient desalination capable of surpassing reverse osmosis in salt removed for a given energy input.

MgSO4 composites in a ferroaluminophosphate for enhancement of volumetric heat storage capacity at a low charging temperature

SummaryFerroaluminophosphate (FAPO4‐5)/MgSO4 composites were prepared as a series of new materials with low charging temperatures and improved volumetric heat storage capacities. A microporous zeolithic compound FAPO4‐5 was used as an adsorbent of water vapor and a matrix of MgSO4 salt particles. Composites with various MgSO4 contents (5‐40 wt%) were then prepared using a wet impregnation method. The MgSO4 salt particles were impregnated into the micropores and textural pores of FAPO4‐5 without the crystal structure of the host material, confirmed by XRD patterns. Although nitrogen adsorption isotherms of the composites showed approximately a half of FAPO4‐5 pore was blocked by MgSO4, the water uptake of the composites reached the sum of those from FAPO4‐5 and MgSO4. The dehydration temperature of MgSO4 in the FAPO4‐5 matrix decreased with its decreasing content due to the easier dehydration of FAPO4‐5. The heat storage recovery of the 25 wt% loaded sample at 80°C was 85.5% while that of MgSO4 was 52.2%. The swelling and agglomeration of the composites containing 25 wt% and less salt were suppressed by the micro and textural pores of FAPO4‐5. The composite at 25 wt% of MgSO4 loading exhibited a total volumetric heat storage capacity of 174 kW h m−3 based on the volume in the hydrated state.

Tailored transition temperature plastic crystals with enhanced thermal energy storage capacity

Pentaerythritol (PE), pentaglycerine (PG), and neopentylglycol (NPG) are non-ionic plastic crystal with high potential for latent heat thermal energy storage (TES) in solar heating applications. These molecules undergo reversible solid phase transitions with unusually large enthalpy of transition (110 J/g - 300 J/g) in the temperature range from 44 °C to 185 °C. To further enhance their heat storage capacity while lowering their price and preserving the advantage of solid phase transitions, a new class of shape-stabilized phase change materials (SSPCMs) in which a polyalcohol with adjustable solid phase transition properties (NPG/PG or PE/PG mixture) supports a cheaper and with higher latent heat solid-liquid PCM (paraffin wax) is proposed in this work. Combined with properly chosen paraffin waxes, NPG/PG mixtures allow tailoring the working temperature of corresponding SSPCMs between 24 °C and 81 °C, whereas PE/PG mixtures allow SSPCMs with phase change adjusted within 81 °C–190 °C temperature range. Produced SSPCMs were thoroughly characterized and their efficiency in terms of heat storage capacity and delivered power upon heat discharge were evaluated. The results achieved show proper anti-leakage effect due to good wettability between paraffins and polyalcohols and inner microstructure of SSPCMs promoting capillarity. In addition, volumetric latent heat storage capacity has been proven to be enhanced up to 45% compared to pure polyalcohols without detrimental effect in discharging power.

Rechargeable proton exchange membrane fuel cell containing an intrinsic hydrogen storage polymer

Proton exchange membrane fuel cells (PEMFCs) are promising clean energy conversion devices in residential, transportation, and portable applications. Currently, a high-pressure tank is the state-of-the-art mode of hydrogen storage; however, the energy cost, safety, and portability (or volumetric hydrogen storage capacity) presents a major barrier to the widespread dissemination of PEMFCs. Here we show an ‘all-polymer type’ rechargeable PEMFC (RCFC) that contains a hydrogen-storable polymer (HSP), which is a solid-state organic hydride, as the hydrogen storage media. Use of a gas impermeable SPP-QP (a polyphenylene-based PEM) enhances the operable time, reaching up to ca. 10.2 s mgHSP−1, which is more than a factor of two longer than that (3.90 s mgHSP−1) for a Nafion NRE-212 membrane cell. The RCFCs are cycleable, at least up to 50 cycles. The features of this RCFC system, including safety, ease of handling, and light weight, suggest applications in mobile, light-weight hydrogen-based energy devices.

Experimental Analysis of Salt Hydrate Latent Heat Thermal Energy Storage System With Porous Aluminum Fabric and Salt Hydrate as Phase Change Material With Enhanced Stability and Supercooling

Abstract Phase change materials (PCMs), especially salt hydrates possess high volumetric energy storage capacity in their transition temperature range. These materials are used in applications where it is necessary to store thermal energy due to temporary load shift between demand and availability. Thus, possible applications are HVAC, recovery of waste heat, and defense thermal management. Despite salt hydrates potential, the practical feasibility of latent heat storage with salt hydrates is limited due to low power rating, supercooling, phase segregation, and long-term stability. Its low power rating and long-term stability limits its application in most applications. This work experimentally validates the stability and thermal performance of a compact heat exchanger charged with salt hydrate during melting and freezing. The compact heat exchanger was designed with fins on both the heat transfer fluid (HTF) and salt hydrate PCM side. The thermal performance of the latent heat thermal energy storage system (LHTESS) was evaluated for various operating conditions. The results show that LHTESS could achieve an average heat transfer coefficient of 124 and 87 W/(m2 K) during melting and solidification, respectively. The stability of the system in suppressing supercooling was validated over 800 cycles with nucleating agent and active homogenous nucleation techniques. The supercooling was reduced to 3 °C with zinc hydroxyl nitrate as nucleating agent and less than 1 °C with the active homogenous nucleation technique. The LHTESS showed less than 6% degradation in energy storage capacity over 800 cycles.

Enhanced thermodynamic properties of ZrNiH3 by substitution with transition metals (V, Ti, Fe, Mn and Cr)

First-principles calculations based on Plane-Wave Self-Consistent Field (PWSCF) method, implemented in quantum espresso program, have been performed on ZrNiH3 substituted with transition metals (V, Ti, Fe, Mn, and Cr). The study aims to investigate the heat of formation in terms of material stability and desorption temperature. It is found that the substitution by transition metals, results in a significant enhancement in the thermodynamic properties accompanied by an increase of the volumetric and gravimetric hydrogen storage capacities. In addition, the obtained values of heat of formation and desorption temperature corroborate with that required by the U.S. Department of Energy (DOE) for stability and volumetric capacity criteria. Moreover, Mn and Fe elements are found to present the lowest substituting content (34%) to obtain optimum hydrogen storage characteristics (enthalpy of formation of - 40 kJ/mol.H2, decomposition temperature of 300 K and volumetric capacity of 134 g.H2/l), without affecting the electronic structure and the metallic character of ZrNiH3.

Using Low-Pressure Methane Adsorption Isotherms for Higher-Throughput Screening of Methane Storage Materials.

A useful correlation between the low-pressure (up to 1.2 bar), low-temperature (195 K) and high-pressure (up to 65 bar), room temperature (298 K) methane storage properties of a range of porous materials is reported. Methane isotherms under these two sets of conditions show a remarkable agreement in both equilibrium adsorption and deliverable capacities for materials with pore volumes that are less than approximately 0.80 cm3/g. This trend holds well for the suite of metal-organic frameworks and porous coordination cages we studied, in addition to a zeolite and porous organic cage. Although it is well known that gravimetric gas storage capacity trends with gravimetric surface area, the 1.2 bar, 195 K excess adsorption capacity of a given framework is a better indicator of its room temperature, 65 bar capacity. Given the significantly smaller sample quantities needed for low-pressure measurements, greater accessibility to researchers around the world, accuracy of the measurement, and higher throughput, we envision this method as a rapid screening tool for the identification of methane storage materials. As excess/total adsorption and gravimetric/volumetric adsorption can be interconverted by simple utilization of the scalar quantities of pore volume or density, respectively, this method can be easily adapted to obtain both gravimetric and volumetric total adsorption capacities for a given adsorbent. In terms of volumetric methane adsorption, we further investigate the relationship between crystallographic and bulk density for the adsorbents studied here. With this analysis, it becomes apparent that in the absence of novel synthetic approaches, reported volumetric storage capacities should be viewed as an optimistic upper limit for a given material and not necessarily a true reflection of its actual adsorption properties as most MOFs have bulk densities that are less than half of their crystallographic values.

Revealing enhancement mechanism of volumetric hydrogen storage capacity of nano-porous frameworks by molecular simulation

In the past decade, nano-porous frameworks (NPFs) have been rapidly developed and considered as the most promising hydrogen storage materials, due to their unique high surface areas and high pore volumes. However, the development and design of NPFs with balanced gravimetric and volumetric H2 storage capacities are still facing a challenge. In this work, 103 porous materials with 34 topologies promising for application in hydrogen storage were theoretically constructed by using experimentally available organic linkers and geometrically optimized further on the basis of molecular mechanics and density functional theory. They were then computationally screened using the grand ensemble Monte Carlo (GCMC) simulations to search the optimal candidates for hydrogen storage under specific conditions. The seven selected NPFs such as SRS_PAF-1 with high-performance hydrogen storage were evaluated and identified on the basis of gravimetric and volumetric H2 storage capacity. Based on univariate analysis, we examined the relationship between the structural characteristics of all these NPFs and their hydrogen storage capacity, and elucidated the correlations between the structural descriptors (ϕ, ρ, Vp, LCD, PLD, GSA, and VSA) by the principal components analysis. Compared with the benchmark MOFs such as NU-1103, SNU-70 and PCN-610, SRS_PAF-1 exhibit the balanced deliverable gravimetric and volumetric H2 storage capacity of 21.8 wt% and 38.0 g L−1, respectively. BOR-TTEI exhibits the highest gravimetric hydrogen storage capacity of 11.3 wt% at ambient temperature and 100 bar. Moreover, PCN-250 and PPN-6 were taken as examples to investigate the enhancement effect of powder compression and network interpenetration on volumetric hydrogen storage performance (Nv) of NPFs. The results indicate that powder compression can efficiently improve their Nv, but the effect of network interpenetration on Nv depends on the length of the organic linker. In a word, those molecular insight into the relationship between the structural characteristics of NPFs and hydrogen storage capacity will help experimental chemists design and synthesize new NPFs with high-performance for hydrogen and other gas storage.