THE EFFECT OF PORE SIZE ON THE ADSORPTION OF GASES WITHIN METAL ORGANIC FRAMEWORKS

The discovery of Metal-Organic Frameworks (MOFs) has brought great excitement to the world of chemistry, as these selective, tunable, porous crystalline structures are highly efficient at carbon capture at low energies. MOFs are also recyclable and have low desorption energies adding to their appeal. They are doubly attractive as most current carboncapture techniques are energy intensive, and as such very costly. Using 690 structures from the CRAFTED database, we carriedout Grand Canonical Monte Carlosimulations (UFF force field, DDEC charges, 1 atm) to quantify how thepore‑limitingdiameter (PLD) that maximises uptake shifts with temperature. For CO₂ we find optimal PLDs of 9.16 Å at 273 K, 8.53 Å at 298 K and 7.77 Å at 323 K. N₂ shows optimal PLDs of 7.55 Å at 273 K, 7.93 Å at 298 K and 8.42 Å at 323 K.Plotting uptake as a function of the dimensionless ratio PLD/σ_adso, where σ_adso isthe Lennard‑Jones diameter of the adsorbate, collapses both gases onto a universal curve whose maximum occursat PLD/σ_adso ≈ 3.4 ± 0.2. This simple design rule provides an immediate screening filter for machine‑learningworkflows that search vast MOF libraries.