Notes and references
z The space group of PCN-122 is I41cd (a = 23.394 A, c = 49.524 A,
V = 27102.9 A3). Co1 has an octahedral coordination geometry with
mixed functional groups, one pyridyl N atom, four carboxylate oxygen
atoms and one aqua ligand (Fig. S4, ESIw). Co1 is connected with Co1
in the other asymmetric unit through one aqua ligand and two
carboxylates from two different ligands.
1 (a) B. Moulton and M. J. Zaworotko, Chem. Rev., 2001, 101, 1629;
(b) D. Zhao, D. J. Timmons, D. Yuan and H.-C. Zhou, Acc. Chem.
Res., 2010, 44, 123; (c) S. Kitagawa, R. Kitaura and S. Noro,
Angew. Chem., Int. Ed., 2004, 43, 2334.
2 (a) C. Janiak, Dalton Trans., 2003, 2781; (b) R. J. Kuppler,
D. J. Timmons, Q. R. Fang, J. R. Li, T. A. Makal,
M. D. Young, D. Q. Yuan, D. Zhao, W. J. Zhuang and
H.-C. Zhou, Coord. Chem. Rev., 2009, 253, 3042; (c) U. Mueller,
M. Schubert, F. Teich, H. Puetter, K. Schierle-Arndt and J. Pastre,
J. Mater. Chem., 2006, 16, 626.
3 (a) D. Zhao, D. Q. Yuan and H.-C. Zhou, Energy Environ. Sci., 2008,
1, 222; (b) S. Q. Ma and H.-C. Zhou, Chem. Commun., 2010, 46, 44;
(c) M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J. Wachter, M. O’Keeffe
and O. M. Yaghi, Science, 2002, 295, 469; (d) L. J. Murray, M. Dinca
and J. R. Long, Chem. Soc. Rev., 2009, 38, 1294.
4 (a) J.-R. Li, R. J. Kuppler and H.-C. Zhou, Chem. Soc. Rev., 2009,
38, 1477; (b) J.-R. Li, Y. Ma, M. C. McCarthy, J. Sculley, J. Yu,
H.-K. Jeong, P. B. Balbuena and H.-C. Zhou, Coord. Chem. Rev.,
2011, 255, 1791.
5 (a) D. Farrusseng, S. Aguado and C. Pinel, Angew. Chem., Int. Ed.,
2009, 48, 7502; (b) A. Corma, H. Garcia and F. X. L. Xamena,
Chem. Rev., 2010, 110, 4606; (c) L. Q. Ma, C. Abney and
W. B. Lin, Chem. Soc. Rev., 2009, 38, 1248.
6 J. Rocha, L. D. Carlos, F. A. A. Paz and D. Ananias, Chem. Soc.
Rev., 2011, 40, 926.
7 G. Ferey, C. Serre, T. Devic, G. Maurin, H. Jobic, P. L. Llewellyn,
G. De Weireld, A. Vimont, M. Daturi and J.-S. Chang, Chem. Soc.
Rev., 2011, 40, 550.
8 D. M. D’Alessandro, B. Smit and J. R. Long, Angew. Chem., Int.
Ed., 2010, 49, 6058.
9 (a) M. Hirscher, Angew. Chem., Int. Ed., 2011, 50, 581;
(b) J. Sculley, D. Yuan and H.-C. Zhou, Energy Environ. Sci.,
2011, 4(8), 2721.
Fig. 4 The low pressure H2 uptake in PCN-121 at 77 K and 87 K.
This relatively high CO2 adsorption is a result of strong
interaction between CO2 (having a high quadruple moment)
and pore surface of the MOF. Presumably, the non-coordinated
N atoms (Lewis base site) of dcbp2ꢁ ligands in the wall may have
played a role in these interactions.18 The heats of adsorption of
CO2 and CH4 were 23.0 and 15.1 kJ molꢁ1, respectively.
H2 adsorption isotherms at 77 and 87 K were also measured
(Fig. 4). The uptakes of 1.4 wt% at 77 K and 1 wt% at 87 K
led to a heat of hydrogen adsorption of 6.63 kJ molꢁ1
consistent with literature values.9
,
To confirm the oxidation state of the Co atoms, magnetic
susceptibility data were collected for crystalline sample of
PCN-121. The data were not field dependent (Fig. S8, ESIw).
The wT product at 300 K has a value of 6.4 cm3 K molꢁ1, in
agreement with the expected for three Co(II) ions in a distorted
octahedral coordination environment with strong spin–orbit
coupling. In a magnetization vs. field plot at 2 K, each Co(II)
ion behaves as an effective S = 1/2. The magnetization does
not saturate, and it reaches a value of 2.5 at 5 T, indicating a
non-zero spin ground state for the tricobalt repeating unit of
PCN-121 with anisotropy and low lying excited states. This is
in agreement with the structural parameters of PCN-121.
PCN-121 consists of infinite chains of tricobalt units, where
the three Co(II) ions are bridged by a m3-OH and various
O atoms from the carboxylate groups.
10 S. S. Han, J. L. Mendoza-Cortes and W. A. Goddard Iii, Chem.
Soc. Rev., 2009, 38, 1460.
11 J. K. Schnobrich, O. Lebel, K. A. Cychosz, A. Dailly, A. G. Wong-Foy
and A. J. Matzger, J. Am. Chem. Soc., 2010, 132, 13941.
12 (a) L. Han and M. Hong, Inorg. Chem. Commun., 2005, 8, 406;
(b) X. Xi, Y. Fang, T. Dong and Y. Cui, Angew. Chem., Int. Ed.,
2011, 50, 1154.
13 (a) D. F. Sun, Y. Ke, D. J. Collins, G. A. Lorigan and H.-C. Zhou,
Inorg. Chem., 2007, 46, 2725; (b) Y. Ke, D. J. Collins, D. F. Sun
and H.-C. Zhou, Inorg. Chem., 2006, 45, 1897.
14 L. Hou, W. X. Zhang, J. P. Zhang, W. Xue, Y. B. Zhang and
X. M. Chen, Chem. Commun., 2010, 46, 6311.
15 M. K. Sharma, I. Senkovska, S. Kaskel and P. K. Bharadwaj,
Inorg. Chem., 2010, 50, 539.
16 H. Abourahma, B. Moulton, V. Kravtsov and M. J. Zaworotko,
J. Am. Chem. Soc., 2002, 124, 9990.
17 K. Biradha, C. Seward and M. J. Zaworotko, Angew. Chem., Int.
Ed., 1999, 38, 492.
18 R. Vaidhyanathan, S. S. Iremonger, G. K. H. Shimizu, P. G. Boyd,
S. Alavi and T. K. Woo, Science, 2010, 330, 650.
In summary, a helical-chain Co(II)-based MOF has been
synthesized. The structure of this MOF contains unusual
M–O–M clusters in its helical chain building units, which are
responsible for the observed magnetic properties. Selective
adsorption of CO2 over CH4 was demonstrated using a
quickly activated sample. Remarkably, PCN-121 exhibits a
facile transition from micro- to meso-porosity depending on the
methods of activation. Mechanistic studies using time-resolved
PXRD techniques are currently under way.
We acknowledge the U.S. Department of Energy (DOE DE-
SC0001015, DE-FC36-07GO17033, and DE-AR0000073), the
National Science Foundation (NSF CBET-0930079), and the
Welch Foundation (A-1725) for financial support to HCZ, as
well as Spanish Government (Grant CTQ2006/03949BQU and
19 (a) Q.-R. Fang, T. A. Makal, M. D. Young and H.-C. Zhou,
Comments Inorg. Chem., 2010, 31, 165; (b) X. S. Wang, S. Q. Ma,
D. F. Sun, S. Parkin and H. C. Zhou, J. Am. Chem. Soc., 2006,
128, 16474; (c) D. Yuan, D. Zhao, D. J. Timmons and H.-C. Zhou,
Chem. Sci., 2011, 2, 103.
´
Ramon y Cajal contract) for financial support to ECS.
c
This journal is The Royal Society of Chemistry 2012
Chem. Commun., 2012, 48, 883–885 885