A series of s-block (Ca, Sr and Ba) metal–organic frameworks: synthesis and structure–property correlation

Abstract

A series of metal-organic frameworks based on alkaline earth metal ions (Ca, Sr and Ba) and 1,3,5benzenetribenzoic acid (BTB) have been synthesized and characterized. These are [H 2 NIJCH 3 ) 2 ]ijCa 7 IJBTB) 5 - 3). All the structures are three-dimensional in nature with different secondary building units. Compound 1 contains one-dimensional Ca-O-Ca zigzag chains while compound 2 contains Sr 5 O 28 pentameric clusters and compound 3 contains one-dimensional Ba-O-Ba chains. Both compounds 1 and 3 form (3,6)-net connectivity while compound 2 forms (3,12)-net connectivity. Optical band gap energy measurements show that compound 1 (2.65 eV) has low band gap energy compared to 2 (3.22 eV) and 3 (3.32 eV). This variation in band gap energy may be due to the difference in structural arrangement. Compound 3 crystallizes in a non-centrosymmetric space group (Pna2 1 ), which belongs to the polar point group C 2v . This compound displays a strong SHG response and good ferroelectric and piezoelectric properties.

Ferroelectricity in Metal–Organic Frameworks: Characterization and Mechanisms

“…7 pC/N . Similarly, there is only one report in which PFM was performed on an MOF . However, the details of the measurement and the method employed to exclude the non‐ferroelectric contributions in the PFM signal were not discussed.…”

Complete Transmetalation in a Metal–Organic Framework by Metal Ion Metathesis in a Single Crystal for Selective Sensing of Phosphate Ions in Aqueous Media

“…Recently we reported a three‐dimensional porous MOF, [H 2 N(CH 3 ) 2 ][Ba(H 2 O)(BTB)], 1 , constructed from an alkaline earth metal ion and 1,3,5‐benzenetribenzoic acid ligand. Herein we show that this compound undergoes metal exchange with the Tb 3+ ion at the metal node in a SC to SC fashion to form [Tb(H 2 O)(BTB)] ( 2 ).…”

Selective CO2 adsorption in water-stable alkaline-earth based metal–organic frameworks

“…5,6 Therefore, alkaline-earth ions are usually regarded as unsuitable metal nodes for forming porous structures. Recent studies, however, show the potential of alkaline-earth based MOFs with specific properties, including ionic conduc-tivity, 7 good ferroelectricity and piezoelectricity, 8 luminescence 9 and gas separation properties. 10 Using alkalineearth ions offers other advantages compared to the transition and lanthanide metal ions, including abundance, light weight and low costs.…”