MOF Methane Storage: Deliverable Capacity

Pressure-Swing Cycle

Charge pressure P_ads 65 bar

Discharge pressure P_des 5.8 bar

Temperature T 298 K

Langmuir Isotherm

Live Readouts

Uptake at P_ads

–

Residual at P_des

–

Deliverable capacity Δn

–

Volumetric density (MOF vs. empty tank)

–

How it works

A metal-organic framework is a crystalline lattice of metal nodes bridged by organic linkers, riddled with nanometre-scale pores (typically 0.5–3 nm). Gas molecules physisorb onto the huge internal surface (often 1,000–7,000 m²/g) via weak van der Waals forces, so a tank packed with MOF holds far more gas at a given pressure than an empty tank of compressed gas alone — the basis of adsorbed natural gas (ANG) storage.

Single-site uptake follows the Langmuir isotherm:

n(P) = n_max · b·P / (1 + b·P)
b(T) = b0 · exp(-ΔH_ads / R·T)

where n_max is the saturation uptake (monolayer capacity), b is the temperature-dependent affinity constant, ΔH_ads is the (negative) isosteric heat of adsorption, and R is the gas constant. Because b falls as T rises, uptake at fixed pressure drops with temperature — visible directly on the isotherm curve.

What a storage tank actually delivers over one charge/discharge cycle is not the total uptake but the deliverable (working) capacity:

Δn = n(P_ads) − n(P_des)

Gas trapped below the discharge pressure never leaves the tank, so a MOF with very strong binding (large ΔH_ads) can actually deliver less usable gas than a moderately-binding one, even though its total uptake is higher — the residual at P_des is adsorbed too tightly to release. This is the central design trade-off in MOF gas-storage materials, set by the U.S. DOE ARPA-E MOVE targets used across the field (P_ads ≈ 65 bar, P_des ≈ 5.8 bar).

Charge / discharge pressure sliders — set the two ends of the pressure-swing cycle; the shaded band on the isotherm shows the deliverable capacity Δn as the vertical drop between them.
Temperature slider — shifts the whole isotherm via the Arrhenius-like b(T) term.
MOF ON/OFF — compares the lattice-adsorbed gas (instanced molecules pinned near lattice nodes, density set by the isotherm) against a pure compressed-gas tank at the same pressure (ideal-gas density only) so the volumetric storage advantage is visible directly in the 3D scene.
Run cycle — animates one charge → discharge sweep, with molecules appearing/disappearing on the lattice as pressure ramps between P_des and P_ads.

MOF lattice node Adsorbed CH₄ Free (gas-phase) CH₄

⚠ Couldn't load the 3D engineThree.js failed to load from the CDN. Check your connection and reload.

MOF Methane Storage: Deliverable Capacity & Pressure-Swing Cycling