Anion-induced morphology control of Al-fumarate MOFs via synergetic coordination and hydrogen bond effects for graded dehumidification

Abstract

Metal organic framework (MOF) dehumidifier presents vast application value to alleviate the humidity stress to improve the comfort of humans. Aluminum-fumarate based MOFs (AF-MOFs) are expected as an important class in this field since their flexibility allows the water adsorption properties to be tunable from the molecular level of the inorganic node and/or organic linkers. Here, AF-MOFs samples were prepared using aluminum salts containing different anions (SO42−, Cl−, NO3−) to reveal how the anion components affect their morphology and thereby disclose the relationship between their structures and activities of water absorption. Systematic characterizations demonstrated that the anions achieved fine morphology control of AF-MOF samples without changing their basic framework, wherein the coordination effect between aluminum atoms in MOF units and atoms in anions (such as oxygen and nitrogen) induced this process. What's more, the water adsorption experiments revealed that by means of the collaborative assistance of specific surface area, hydrogen bond interaction and/or coordination effects, the SO42−, Cl− and NO3− induced AF-MOFs reveal optimal water absorption performance at low, medium and high relative pressure, respectively. With no complex steps, extra morphology modulators and harsh temperature/pressure, this study provides an environmentally friendly new sight for regulating the morphology of AF-MOFs to optimize their dehumidification abilities.