Donor‐Acceptor Stacks in Flexible Porous Coordination Polymers Toward Room‐Temperature Ferroelectricity

Abstract

ABSTRACT Ferroelectricity has long been of great scientific interest due to its tremendous potential for information storage technologies and wide‐ranging applications. Metal‐organic frameworks (MOFs) or porous coordination polymers (PCPs), with their structural tunability and dynamic host‐guest chemistry, offer a powerful platform for engineering next‐generation ferroelectrics. However, progress in ferroelectric MOFs/PCPs has been limited by their intrinsically weak polarization, restricting the realization of non‐trivial switchable ferroelectricity feasible at room temperature. We address this limitation, reporting a series of flexible PCPs with mixed donor‐acceptor (D‐A) stacks designed to achieve room‐temperature ferroelectricity via strong charge‐transfer interactions. The 3D Zn‐based PCP, {[Zn( o ‐phen)(2,6‐ndc)]·DMF} n , having a supramolecular dynamic nano‐space for D‐A stacking, exhibits intrinsic flexibility that endows structural adaptation to the guest molecules of varying shape, size, and chemical nature. The encapsulation of electron‐rich aromatic amine guests like N , N ′‐dimethyl aniline and N , N ′‐dimethyl‐ p ‐toluidine results in the formation of extended D‐A stacks with acceptor motifs of the framework along a particular crystallographic axis. Peierls‐like distortion of these 1D extended D‐A stacks gives rise to spontaneous polarization, ultimately resulting in room‐temperature ferroelectricity. We furthermore show that the ferroelectric features of the PCP are closely related to the packing and geometry of the guest molecules incorporated.