Concomitant Photoresponsive Chiroptics and Magnetism in Metal-Organic Frameworks at Room Temperature

Abstract

Stimulus-responsive metal-organic frameworks (MOFs) can be used for designing smart materials. Herein, we report a family of rationally designed MOFs which exhibit photoresponsive chiroptical and magnetic properties at room temperature. In this design, two specific nonphotochromic ligands are selected to construct enantiomeric MOFs, {Cu2(L-mal)2(bpy)2(H2O)·3H2O}n (1) and {Cu2(D-mal)2(bpy)2(H2O)·3H2O}n (2) (mal=malate, bpy=4,4’−bipyridine), which can alter their color, magnetism, and chiroptics concurrently in response to light. Upon UV or visible light irradiation, long-lived bpy− radicals are generated via photoinduced electron transfer (PET) from oxygen atoms of carboxylates and hydroxyl of malates to bpy ligands, giving rise to a 23.7% increase of magnetic susceptibility at room temperature. The participation of the chromophores (-OH and -COO−) bound with the chiral carbon during the electron transfer process results in a small dipolar transition; thus, the Cotton effects of the enantiomers are weakened along with a photoinduced color change. This work demonstrates that the simultaneous responses of chirality, optics, and magnetism can be achieved in a single compound at room temperature and may open up a new pathway for designing chiral stimuli-responsive materials.

Precise Construction of Stable Bimetallic Metal–Organic Frameworks with Single-Site Ti(IV) Incorporation in Nodes for Efficient Photocatalytic Oxygen Evolution

“…Metal-organic frameworks (MOFs), an emerging class of porous crystalline materials scaffolded by metal ion/cluster nodes and organic ligands in long-range order, can integrate targeted reactive organic and inorganic species into structures with clear structural information. [9][10][11][12][13] In this regard, MOFs built by the coordination of Co clusters and photo-responsive organic molecules would be an ideal photocatalyst candidate overcoming the difficulties in other Co catalysts mentioned above. 14,15 In addition, the intrinsic porosity of MOFs permits complete exposure of each orderly monodispersed Co clusters accessible to the substrate molecules to facilitate photocatalytic water oxidation.…”

Room-Temperature Magnetoelectric Coupling in Electronic Ferroelectric Film based on [(n-C3H7)4N][FeIIIFeII(dto)3] (dto = C2O2S2)

“…In contrast, investigations on CO multiferroics have been extended to molecular-based compounds in recent years, − due to the outstanding advantages of molecular-based compounds, such as diversity and adjustable structure, mild synthesis conditions, and ease of processing. − Actually, among the molecular-based compounds, the intra- and intermolecular electron transfer can be easily induced by valence instability or bistability through external stimuli, such as changes in temperature, pressure, or light irradiation. , Most importantly, valence instability or bistability-induced electron hopping can yield ferroelectric polarization (i.e., electron ferroelectricity) and further realize ME coupling. However, to date, there have been no multiferroic/ME-related investigations on molecular-based CO multiferroic materials or on their thin film samples.…”

“…30−32 Actually, among the molecular-based compounds, the intra-and intermolecular electron transfer can be easily induced by valence instability or bistability through external stimuli, such as changes in temperature, pressure, or light irradiation. 33,34 Most importantly, valence instability or bistability-induced electron hopping can yield ferroelectric polarization (i.e., electron ferroelectricity) and further realize ME coupling. However, to date, there have been no multiferroic/ME-related investigations on molecular-based CO multiferroic materials or on their thin film samples.…”

Harnessing Electrostatic Interactions for Enhanced Conductivity in Metal-Organic Frameworks

“…Exploration of electrically conductive metal-organic frameworks (MOFs) [1] offers exciting opportunities for fabricating electronic materials with the advantages of tunable structure, high crystallinity, and permanent porosity [2]. This would greatly expand the prospective applications of MOF materials [3][4][5][6][7][8][9][10][11][12][13]. Although increasing endeavors have been devoted to this field [14][15][16][17], MOFs with high conductivity are still rare, and the preparation of conductive MOFs has remained a big challenge to date.…”