Laybourn Andrea, Katrib Juliano, Palade Paula A, Easun Timothy L, Champness Neil R, Schröder Martin, Kingman Samuel W
School of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK and Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK.
Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK.
Phys Chem Chem Phys. 2016 Feb 21;18(7):5419-31. doi: 10.1039/c5cp05426e.
Preparation of metal organic frameworks (MOFs) via microwave heating is becoming increasingly popular due to reduced reaction times and enhanced control of MOF particle size. However, there is little understanding about the detailed interaction of the electric field portion of the wave with reactants during the synthesis of MOFs. In order to overcome this lack of fundamental understanding, information about the dielectric properties of the reactants is required. In this work the dielectric constants (ε') and loss factors (ε'') of benzene-1,4-dicarboxylic acid (H2BDC; also known as terephthalic acid) and a number of M(III) (M = metal) salts dissolved in deionized water were measured as a function of frequency, temperature and concentration and with varying anions and cations. Dielectric data confirm the aqueous M(III) salts to be strong microwave absorbers, particularly at 915 MHz. M(III) salts with mono-anionic ligands (for example chlorides and nitrates) exhibit higher losses than di-anionic salts (sulfates) demonstrating that the former are heated more effectively in an applied microwave field. Of the M(III) salts containing either singly- or doubly-charged anions, those containing Fe(III) have the highest loss indicating that they will heat more efficiently than other M(III) salts such as Cr(III) and Al(III). Interestingly, H2BDC exhibits little interaction with the electric field at microwave frequencies.
通过微波加热制备金属有机框架材料（MOF）正变得越来越流行，这是因为反应时间缩短且对MOF粒径的控制得到增强。然而，对于MOF合成过程中波的电场部分与反应物之间的详细相互作用，人们了解甚少。为了克服这种对基本原理认识的不足，需要有关反应物介电特性的信息。在这项工作中，测量了溶解于去离子水中的对苯二甲酸（H2BDC；也称为 terephthalic acid）和多种M(III)（M = 金属）盐的介电常数(ε')和损耗因子(ε'')，它们是频率、温度、浓度以及不同阴离子和阳离子的函数。介电数据证实水合M(III)盐是强微波吸收剂，特别是在915 MHz时。具有单阴离子配体的M(III)盐（例如氯化物和硝酸盐）比双阴离子盐（硫酸盐）表现出更高的损耗，这表明前者在施加的微波场中加热更有效。在含有单电荷或双电荷阴离子的M(III)盐中,含有Fe(III)的盐具有最高的损耗，这表明它们比其他M(III)盐（如Cr(III)和Al(III)）加热效率更高。有趣的是，H2BDC在微波频率下与电场的相互作用很小。
