MIL-53(Al)/Carbon Films for CO₂-Sensing at High Pressure

Abstract

Chemiresistive threshold sensor films based on the switchable metal−organic framework (MOF) MIL-53(Al) (MIL = Mateŕiaux de l'Institut Lavoisier) and conductive carbon additives were developed, characterized and successfully applied for selective detection of CO 2 in mixtures with methane at high pressure (up to 25 bar). Two transitions of the crystal structure, from the lp (large pore) form to the np (narrow pore) form at CO 2 partial pressure below 0.5 bar and back to the lp form at ca. 6 bar, also known as "breathing", result in two detectable stepwise resistance changes of sensor film, if CO 2 is present in the mixture with methane. The sensor shows a rapid response of the specific resistance (response time ca. 25 s), which directly correlates to the expected structural change of the switchable MOF. Two films containing carbon or carbon nanotubes as conductive component were compared regarding the influence of the additive particles geometry on sensing performance, showing benefits of the isotropic particle shape. Cyclic sensing measurements proved the durability of the composites.

Collective Breathing in an Eightfold Interpenetrated Metal–Organic Framework: From Mechanistic Understanding towards Threshold Sensing Architectures

“…In general, breathing phenomena associated with pronounced changes of the unit cell volume also cause macroscopically detectable crystal volume changes even in a powdered sample. This feature was recently used for the conceptual design of resistive threshold sensing architectures consisting of carbon nanomaterials (carbon black or carbon nanotubes) and a switchable MOF with significant volume change upon adsorption of n ‐butane or CO 2 . Herein, we employ this general concept by integrating JUK‐8 into electron conductive composite films to generate the first threshold humidity sensor based on a switchable MOF demonstrating pronounced resistivity changes upon reaching the respective humidity threshold.…”

Pillared-layered metal–organic frameworks for mechanical energy storage applications

“…[6][7][8][9]. The drastic change of the volume accompanying the breathing transition makes these peculiar materials extremely enticing for a large variety of applications such as gas storage, separation and detection, [10][11][12] controlled drug release 13 and mechanical energy storage. 14,15 Given these remarkable properties, extensive efforts have also been spent to unravel the origin of exibility from a theoretical point of view.…”

Role of particle size and surface functionalisation on the flexibility behaviour of switchable metal–organic framework DUT-8(Ni)

“…For instance, nely tuned pore sizes and window diameters are used to exclude larger molecules in molecular sieving applications, which is forfeited if the pores can change shape. 7 On the other hand, framework exibility also opens up new applications for MOFs, such as their use in sensory devices, 11,12 advanced gas separations 13 or as carriers for drug delivery. 7,14 In sensing devices, the well-dened topologies and highly porous nature of MOFs means they offer enhanced sensitivity and selectivity towards the analyte.…”