Hysteresis curves reveal the microscopic origin of cooperative CO₂ adsorption in diamine-appended metal–organic frameworks

Diamine-appended metal–organic frameworks (MOFs) of the form Mg2(dobpdc)(diamine)2 adsorb CO2 in a cooperative fashion, exhibiting an abrupt change occupancy with pressure or temperature. This is accompanied by hysteresis. While hysteresis suggestive first-order phase transition, we show that hysteretic temperature-occupancy curves associated this material are qualitatively unlike seen presence transition; they instead consistent chain polymerization, within one-dimensional channels MOF, absence transition. Our simulations microscopic model reproduce dynamics, providing physical understanding adsorption industrially important class materials.