Proton Conduction in Stable, Crystalline, and Porous Hydrogen‐Bonded Metal–Organic Frameworks

Abstract

ABSTRACT Hydrogen‐bonded metal–organic frameworks (HMOFs) represent a novel class of crystalline materials that integrate hydrogen bonds (HBs) and coordination bonds (CBs) within stable structures. Herein, we designed carbonyl‐rich molecules with extended arms to increase the density of hydrogen‐bond acceptors and enhanced benzene ring rotation to reduce π‐π stacking, thereby strengthening hydrogen bonding to assist coordination‐driven assembly of HMOFs. Benefiting from strong hydrogen bonding between central carbonyl groups and metal ions to modulate metal coordination, a series of 2+2 layer‐interpenetrated HMOFs with different metal nodes (Co 2+ , Ni 2+ , and Zn 2+ ) were synthesized. Serving as interpenetration intersections, those metal nodes stabilize the framework via hydrogen bonding, together with the inter‐locked coordination framework and extensive hydrogen‐bonded network, endow the HMOFs with open channels and qualified stability. These HMOFs exhibit proton conductivity of ∼10 −3  S cm −1 at 95°C and 98% relative humidity with activation energies all below 0.2 eV. This study presents a new approach for directly constructing stable HMOFs using carbonyl‐rich planar ligands, providing valuable insights for the rational design and synthesis of stable, highly crystalline frameworks.