Functionalised metal–organic frameworks: a novel approach to stabilising single metal atoms

Abstract

We have investigated the potential of metal–organic frameworks for immobilising single atoms of transition metals using a model system of Pd supported on NH2-MIL-101(Cr).

Effect of linker functionalisation on the catalytic properties of Cu nanoclusters embedded in MOFs in direct CO and CO2 reduction by H2

“…We have previously showed that functionalisation of UiOs may result in enhanced interaction with embedded Pd NCs, and in the potential change of catalytic performance. 32,33 In particular, the effect of amino groups is worth exploring as i) it can form strong interactions with metal NCs embedded in the MOF's pores potentially mimicking SMSIs [32][33][34] , and furthermore ii) it has been shown to interact strongly with CO 2 and thus their presence may be favourable for its activation and conversion. 35 At the same time, linker functionalisation also may have a long-range effect on the inorganic node (i.e.…”

Interactions of Hydrogen with Pd@MOF Composites

“…Since the pristine MIL‐101 was known to have sufficiently high interaction energy with Pd to allow for embedding Pd nanoparticles inside its pores, Szilágyi et al . used the strategy of increasing the MOF−Pd interaction energy to decrease the size of the embedded Pd particle size down to the single‐atom level . This strategy was used in combination with the liquid impregnation method of a suitable Pd precursor (Pd(NO 3 ) 2 or Pd(ac) 2 ) acetonitrile solution, followed by the thorough washing of the sample with acetonitrile to remove any precursor that is not bonded with the functional group, the evaporation of the solvent at elevated temperatures and under dynamic vacuum, and the final reduction of the Pd precursor in an H 2 ‐Ar stream at 200 °C.…”

“…Szilágyi et al . obtained a metal‐organic framework with Pd immobilised on its pores through a mixture of pore filling and as single atoms . The hydrogen uptake characteristics of the composites material reflected 3 types of hydrogen‐sorbent interactions, including adsorption on the MOF matrix, interstitial hydride formation on the larger ( ca .…”

“… Structure of the Pd(H 2 ) complex as calculated with DFT, indicating bond lengths and angles. Figure reproduced from reference with permission.…”

“…Notable exceptions to the above rules are interstitial hydrides, cf . Pd, LaNi 5 , although they form through the dissociation of hydrogen molecules and subsequent occupation of the interstitial spaces by the hydrogen atoms, H in them does not form strong chemical bonds with the metal atoms;,,, additionally, so‐called σ ‐complexes have been reported in which though the hydrogen‐hydrogen bonds are not broken there is evidence of charge transfer between the central transition metal or ion and the hydrogen molecule . Both of these types of bonds result in reversible hydrogen bonds that may form and be bonded near ambient conditions however, reported σ ‐complexes, owing to the necessity of spatial and chemical isolation of the central transition metal atoms or ions have not reached substantial hydrogen uptake yet.…”