Shen Guoqiang, Pan Lun, Zhang Rongrong, Sun Shangcong, Hou Fang, Zhang Xiangwen, Zou Ji-Jun
Key Laboratory for Green Chemical Technology of the Ministry of Education, School of Chemical Engineering and Technology, Collaborative Innovative Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, 300072, China.
Adv Mater. 2020 Mar;32(11):e1905988. doi: 10.1002/adma.201905988. Epub 2020 Feb 5.
Hematite attracts intensive interest as an adsorbent for water purification, but the oversized dimension and inherent high-spin Fe(III) restrict its adsorption capability and kinetics. Herein a spatial-confinement strategy is reported that synthesizes ultrafine α-Fe O benefiting from nanogrids constructed by predeposition of TiO nanodots in the MCM-41 channel, and that tunes the spin-state of Fe(III) from high-spin to low-spin induced by the strong guest-host interaction between the ultrafine Fe O with SiO (MCM-41). The low-spin Fe(III) endorses strong bonding with anionic adsorbates, and significantly facilitates the electrons transfer from Fe O to SiO to form a highly positive charged surface, and thereby shows superior electrostatic multilayer adsorption performance to different kinds of anionic contaminations. Specifically, the maximum uptake, adsorption rate, and distribution coefficient (K ) for Rose Bengal dye reach as high as 1810 mg g , 1644 g (g min) , and 2.2 × 10 L kg , which are more than 8, 230, and 3700 times higher than those of commercial activated carbon, respectively. It also shows outstanding purification performance for real field water. It is demonstrated that a strong guest-host interaction can alter the spin-state of transition metal oxides, which may pave a new way to improve their performance in adsorption and other applications like catalysis.
赤铁矿作为一种用于水净化的吸附剂引起了广泛关注，但其尺寸过大以及固有的高自旋Fe(III)限制了其吸附能力和动力学。本文报道了一种空间限制策略，该策略通过在MCM-41通道中预先沉积TiO纳米点构建纳米网格来合成超细α-Fe₂O₃，并通过超细Fe₂O₃与SiO₂（MCM-41）之间强烈的客体-主体相互作用将Fe(III)的自旋态从高自旋调节为低自旋。低自旋Fe(III)与阴离子吸附质形成强键，显著促进电子从Fe₂O₃转移到SiO₂，形成高正电荷表面，从而对不同种类的阴离子污染物表现出优异的静电多层吸附性能。具体而言，孟加拉玫瑰红染料的最大吸附量、吸附速率和分配系数（Kd）分别高达1810 mg g⁻¹、1644 g (g⁻¹ min⁻¹)和2.2 × 10³ L kg⁻¹，分别比商业活性炭高出8倍、230倍和3700倍以上。它对实际野外水也表现出出色的净化性能。结果表明，强烈的客体-主体相互作用可以改变过渡金属氧化物的自旋态，这可能为提高其在吸附及催化等其他应用中的性能开辟一条新途径。
