Assembly of Solvent-Incorporated Rod Secondary Building Units to Ultramicroporous Metal–Organic Frameworks for Acetylene Purification

Abstract

The process of industrial purification of acetylene (C₂H₂) is crucial yet challenging due to the similarities in physical properties and kinetic molecular sizes between C₂H₂ and the impurity gases generated during its production. Conventional distillation processes frequently result in significant energy waste, highlighting the urgent need for more efficient separation techniques. Metal–organic frameworks (MOFs), as a class of porous physical adsorbents, have demonstrated remarkable success in the separation and purification of light hydrocarbons. By applying the reticular chemistry approach, we have rationally designed and synthesized two isoreticular compounds (named CoTPTA and MnTPTA) with novel low-valent {M–O–M} rod secondary building units (SBUs) based on the tetracarboxylic acid ligand H₄TPTA ([1,1′:3′,1″-terphenyl]-4,4′,4″,6′-tetracarboxylic acid). Both compounds displayed outstanding chemical stability when exposed to various organic solvents. In addition, a series of gas adsorption experiments demonstrated that they both have good C₂H₂ purification ability. The adsorption selectivity was subsequently verified by ideal adsorption solution theory (IAST), where the selectivity of CoTPTA for C₂H₂/CO₂ was 6.65 (v/v = 0.5:0.5).