Restoring Porosity and Uncovering Flexibility in Pillared 3D‐Linker Metal‐Organic Frameworks

Abstract

Abstract Porous adsorbents have emerged as leading materials for carbon capture, where pressure‐controlled regeneration offers a key advantage over energy‐demanding temperature swing adsorption. Flexible metal‐organic frameworks (MOFs) comprised of pillared linkers are proposed to meet this need due to the unique ability to adjust their pores to maximize host‐guest interactions. However, many pillared MOFs show structural collapse following activation. We highlight a new approach to constructing pillared MOFs which retain their porosity upon activation, while also showing flexibility and selective gas adsorption. Two different MOFs were formed using cubane‐1,4‐dicarboxylate (cdc) as a pillar linking zinc triazolate sheets, [Zn 2 (trz) 2 (cdc)] and [Zn 2 (trz) 2 (Br‐cdc)], and their structural framework dynamics investigated using advanced characterization techniques. In situ X‐ray powder diffraction performed in parallel with gas adsorption experiments revealed specific, reversible structural transformations between a narrow pore and open pore phase of the MOFs. These new MOFs reveal a high enthalpy of CO 2 adsorption, driven by interesting network flexibility previously unobserved in the collapsed benzene‐1,4‐dicarboxylate analogue. A combination of experimental techniques and in silico calculations revealed that the phase transformations are governed by local coordination flexibility around the open‐metal site available in [Zn 2 (trz) 2 (cdc)].