Study of the scale-up, formulation, ageing and ammonia adsorption capacity of MIL-100(Fe), Cu-BTC and CPO-27(Ni) for use in respiratory protection filters

Abstract

The metal-organic frameworks (MOFs) MIL-100(Fe), Cu-BTC and CPO-27(Ni) were synthesised in 1 kg batches. The materials were then formed in two different industrially relevant ways. Firstly, dry granulation was used to produce pellets which were sieved to give material with a 300-1000 μm size, and the fines were subsequently recycled to mimic a large scale industrial process. Secondly, wet granulation with a polymer was used to produce granules which were again sieved to 300-1000 μm. XRD data shows that the structures of MIL-100(Fe) and CPO-27(Ni) remain intact during both forming processes, whilst Cu-BTC is shown to degrade during processing. This is in line with the ammonia adsorption data obtained for the formed materials which evaluated the ammonia adsorption capacity of the materials using breakthrough measurements. MIL-100(Fe) and CPO-27(Ni) are shown to have capacities of 47 mg g and 62 mg g respectively whilst Cu-BTC has a decreased capacity of 37 mg g from 97 mg g upon forming. The formed materials were also aged at 25 °C and 80% humidity for a week and the ammonia adsorption capacity re-evaluated. As expected, Cu-BTC decomposed under these conditions, whilst MIL-100(Fe) and CPO-27(Ni) show slightly decreased ammonia adsorption capacities of 36 mg g and 60 mg g respectively.

Unravelling ammonia adsorption mechanisms of adsorbents in humid conditions

“…We also see for Zn-CPO-27 very good agreement with the result obtained by Glover et al [7]: 49 mg/g versus 48 mg/g. A fair matching result is also observed for Cu-BTC provided here by MOFTech and that of Hindocha [16] study (112 mg/g, 105 mg/g). On the other hand, we can acknowledge rather systematic inconsistencies for uptakes on UiO-66 type materials.…”

“…When comparing the NH3 uptake data obtained here with data reported elsewhere, we can observe good agreement in some cases and major apparent inconsistencies in other cases (see table S1 in the SI). Regarding matching measurements, we can cite uptakes for Fe-BTC and Ni-CPO-27 (40 and 58 mg/g), which are similar to those obtained by Hindocha et al [16] (47 and 64 mg/g), keeping in mind that the solids were shaped and tested under slightly different yet comparable conditions. We recall that the Ni-CPO-27 and Fe-BTC solids tested here were supplied by Johnson Matthey [16] in the context of the "PRODIA" EC program for crossed validation purposes.…”

“…Regarding matching measurements, we can cite uptakes for Fe-BTC and Ni-CPO-27 (40 and 58 mg/g), which are similar to those obtained by Hindocha et al [16] (47 and 64 mg/g), keeping in mind that the solids were shaped and tested under slightly different yet comparable conditions. We recall that the Ni-CPO-27 and Fe-BTC solids tested here were supplied by Johnson Matthey [16] in the context of the "PRODIA" EC program for crossed validation purposes. The sample being the same, it is not surprising to find consistent results.…”

“…On the other hand, zeolites perform well in dry conditions but their performance is jeopardised under humid conditions [7]. In contrast, a diverse group of MOFs have shown high NH3 adsorption capacity under dry and also humid conditions, such as CuBTC [13][14] [15], MOF-74 [7], FeBTC [16] and Zr-based MOFs [17]. Based on adsorption simulations at the molecular scale, Snurr [18] and co-workers have suggested that the most appropriate adsorbent should be hydrophobic in order to favour NH3 adsorption versus that of H2O.…”

Adsorption and diffusion of CO2 in CPO-27–Ni beads

“…Metal organic frameworks (MOFs) are a new class of materials, which have a high surface area and a large pore volume (Furukawa et al 2013). Due to these characteristics, these materials have found extensive applications such as gas storage (Gygi et al 2016;Mason et al 2014;Tagliabue et al 2011), heterogeneous catalysis (Pettinari et al 2017;Ranocchiari and van Bokhoven 2011), adsorption desalination (Youssef et al 2017), respiratory filters (Hindocha and Poulston 2017), drug delivery systems (Al Haydar et al 2017;Pettinari et al 2017), sensors (Lustig et al 2017;Pettinari et al 2017), MOF-polymer composites (Zhang et al 2016), etc.…”