TY - JOUR
T1 - Structural reversibility of Cu doped NU-1000 MOFs under hydrogenation conditions
AU - Halder, Avik
AU - Lee, Sungsik
AU - Yang, Bing
AU - Pellin, Michael J.
AU - Vajda, Stefan
AU - Li, Zhanyong
AU - Yang, Ying
AU - Farha, Omar K.
AU - Hupp, Joseph T.
N1 - Funding Information:
The work at Northwestern University was supported by the Inorganometallic Catalyst Design Center, an EFRC funded by the DOE, Office of Basic Energy Sciences (Grant No. DE-SC0012702). The work at Argonne (A.H., B.Y., M.J.P., and S.V.) was supported by the US Department of Energy, BES Materials Sciences, under Contract No. DEAC02–06CH11357 with UChicago Argonne, LLC, operator of Argonne National Laboratory, and the work at the Advance Photon Source (S.L., beamline 12-BM) was supported by the US DOE, Scientific User Facilities, under Contract No. DEAC02-06CH11357. S.V. also acknowledges support from the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement No. 810310, which corresponds to the J. Heyrovsky Chair project (“ERA Chair at J. Heyrovský Institute of Physical Chemistry AS CR – The institutional approach towards ERA”) during the finalization of the paper. The funders had no role in the preparation of the article.
PY - 2020/2/28
Y1 - 2020/2/28
N2 - The metal-organic framework (MOF), NU-1000, and its metalated counterparts have found proof-of-concept application in heterogeneous catalysis and hydrogen storage among others. A vapor-phase technique, akin to atomic layer deposition (ALD), is used to selectively deposit divalent Cu ions on oxo, hydroxo-bridged hexa-zirconium(IV) nodes capped with terminal -OH and -OH2 ligands. The subsequent reaction with steam yields node-anchored, CuII-oxo, hydroxo clusters. We find that cluster installation via AIM (ALD in MOFs) is accompanied by an expansion of the MOF mesopore (channel) diameter. We investigated the behavior of the cluster-modified material, termed Cu-AIM-NU-1000, to heat treatment up to 325 °C at atmospheric pressure with a low flow of H2 into the reaction cell. The response under these conditions revealed two important results: (1) Above 200 °C, the initially installed few-metal-ion clusters reduce to neutral Cu atoms. The neutral atoms migrate from the nodes and aggregate into Cu nanoparticles. While the size of particles formed in the MOF interior is constrained by the width of mesopores (∼3 nm), the size of those formed on the exterior surface of the MOF can grow as large as ∼8 nm. (2) Reduction and release of Cu atoms from the MOFs nodes is accompanied by the dynamic structural transformation of NU-1000 as it reverts back to its original dimension following the release. These results show that while the MOF framework itself remains intact at 325 °C in an H2 atmosphere, the small, AIM-installed CuII-oxo, hydroxo clusters are stable with respect to reduction and conversion to metallic nanoparticles only up to ∼200 °C.
AB - The metal-organic framework (MOF), NU-1000, and its metalated counterparts have found proof-of-concept application in heterogeneous catalysis and hydrogen storage among others. A vapor-phase technique, akin to atomic layer deposition (ALD), is used to selectively deposit divalent Cu ions on oxo, hydroxo-bridged hexa-zirconium(IV) nodes capped with terminal -OH and -OH2 ligands. The subsequent reaction with steam yields node-anchored, CuII-oxo, hydroxo clusters. We find that cluster installation via AIM (ALD in MOFs) is accompanied by an expansion of the MOF mesopore (channel) diameter. We investigated the behavior of the cluster-modified material, termed Cu-AIM-NU-1000, to heat treatment up to 325 °C at atmospheric pressure with a low flow of H2 into the reaction cell. The response under these conditions revealed two important results: (1) Above 200 °C, the initially installed few-metal-ion clusters reduce to neutral Cu atoms. The neutral atoms migrate from the nodes and aggregate into Cu nanoparticles. While the size of particles formed in the MOF interior is constrained by the width of mesopores (∼3 nm), the size of those formed on the exterior surface of the MOF can grow as large as ∼8 nm. (2) Reduction and release of Cu atoms from the MOFs nodes is accompanied by the dynamic structural transformation of NU-1000 as it reverts back to its original dimension following the release. These results show that while the MOF framework itself remains intact at 325 °C in an H2 atmosphere, the small, AIM-installed CuII-oxo, hydroxo clusters are stable with respect to reduction and conversion to metallic nanoparticles only up to ∼200 °C.
UR - http://www.scopus.com/inward/record.url?scp=85080076687&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85080076687&partnerID=8YFLogxK
U2 - 10.1063/1.5130600
DO - 10.1063/1.5130600
M3 - Article
C2 - 32113354
AN - SCOPUS:85080076687
VL - 152
JO - Journal of Chemical Physics
JF - Journal of Chemical Physics
SN - 0021-9606
IS - 8
M1 - 084703
ER -