Moreau Florian, Kolokolov Daniil I, Stepanov Alexander G, Easun Timothy L, Dailly Anne, Lewis William, Blake Alexander J, Nowell Harriott, Lennox Matthew J, Besley Elena, Yang Sihai, Schröder Martin
School of Chemistry, University of Manchester, Manchester M13 9PL, United Kingdom.
Boreskov Institute of Catalysis, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090, Russia.
Proc Natl Acad Sci U S A. 2017 Mar 21;114(12):3056-3061. doi: 10.1073/pnas.1615172114. Epub 2017 Mar 9.
Modulation and precise control of porosity of metal-organic frameworks (MOFs) is of critical importance to their materials function. Here we report modulation of porosity for a series of isoreticular octacarboxylate MOFs, denoted MFM-180 to MFM-185, via a strategy of selective elongation of metal-organic cages. Owing to the high ligand connectivity, these MOFs do not show interpenetration, and are robust structures that have permanent porosity. Interestingly, activated MFM-185a shows a high Brunauer-Emmett-Teller (BET) surface area of 4,734 m g for an octacarboxylate MOF. These MOFs show remarkable CH and CO adsorption properties, notably with simultaneously high gravimetric and volumetric deliverable CH capacities of 0.24 g g and 163 vol/vol (298 K, 5-65 bar) recorded for MFM-185a due to selective elongation of tubular cages. The dynamics of molecular rotors in deuterated MFM-180a-d and MFM-181a-d were investigated by variable-temperature H solid-state NMR spectroscopy to reveal the reorientation mechanisms within these materials. Analysis of the flipping modes of the mobile phenyl groups, their rotational rates, and transition temperatures paves the way to controlling and understanding the role of molecular rotors through design of organic linkers within porous MOF materials.
金属有机框架材料（MOFs）孔隙率的调控与精确控制对其材料功能至关重要。在此，我们报道了通过一种选择性延长金属有机笼的策略，对一系列等规八羧酸MOFs（命名为MFM - 180至MFM - 185）的孔隙率进行调控。由于配体的高连接性，这些MOFs不显示互穿结构，且是具有永久孔隙率的坚固结构。有趣的是，对于一种八羧酸MOF，活化后的MFM - 185a展现出高达4734 m²/g的 Brunauer - Emmett - Teller（BET）比表面积。这些MOFs表现出显著的CH₄和CO₂吸附性能，特别是由于管状笼的选择性延长，MFM - 185a在298 K、5 - 65 bar条件下记录到同时具有0.24 g/g的高重量法和163 vol/vol的体积法可输送CH₄容量。通过变温¹H固体核磁共振光谱研究了氘代MFM - 180a - d和MFM - 181a - d中分子转子的动力学，以揭示这些材料内部的重排机制。对移动苯基的翻转模式、旋转速率和转变温度的分析，为通过设计多孔MOF材料中的有机连接体来控制和理解分子转子的作用铺平了道路。
