Template-directed Synthesis of Three Metal Oxalates via 4-Connected Building Units

Three novel compounds, [Co（en）3]2[Zr2（C2O4）7]·2H20（HNU-2, en=ethylenediamine）, [Co（NH3）6]· [Ce（CzO4）3（H2O）]·H2O（HNU-3） and [Co（dien）2][Gd（C2On）3]·0.75H2O（HNU-4, dien=dethylenetriamine） were hydro- thermal synthesized based on the templates of [Co（en）3]C13, [C0（NH3）6]C13 and [Co（dien）2]C13, respectively. The Zr4＋ Ce3＋ and Gd3＋ cations are all coordinated by four oxalates to form [M（C2O4）n（H2O）n]m （M=Zr, Ce or Gd; n=0 or 1; m=4 or 5）, which are similar to [In（C2O4）4]5- in NKB-1, and can be regarded as 4-connected building units. The [M（C2O4）a（H2O）n]m units are connected via sharing the bis-bidentate bridging oxalate ligands to form binuclears in HNU-2 and 1D ＂zigzag＂ chains in HNU-3 and HNU-4. cular building units to design 3D open frameworks with It is suggested that these compounds could be used as mole- zeolite topologies.

Ultra-Low-Dose Pre-Metallation Strategy Served for Commercial Metal-Ion Capacitors

Sacrificial pre-metallation strategy could compensate for the irreversible consumption of metal ions and reduce the potential of anode,thereby elevating the cycle performance as well as open-circuit voltage for full metal ion capacitors(MICs).However,suffered from massive-dosage abuse,exorbitant decomposition potential,and side effects of decomposition residue,the wide application of sacrificial approach was restricted.Herein,assisted with density functional theory calculations,strongly coupled interface(M-O-C,M=Li/Na/K)and electron donating group have been put forward to regulate the band gap and highest occupied molecular orbital level of metal oxalate(M_(2)C_(2)O_(4)),reducing polarization phenomenon and Gibbs free energy required for decomposition,which eventually decrease the practical decomposition potential from 4.50 to 3.95 V.Remarkably,full sodium ion capacitors constituted of commercial materials(activated carbon//hard carbon)could deliver a prominent energy density of 118.2 Wh kg^(−1)as well as excellent cycle stability under an ultra-low dosage pre-sodiation reagent of 15-30 wt%(far less than currently 100 wt%).Noteworthily,decomposition mechanism of sacrificial compound and the relative influence on the system of MICs after pre-metallation were initially revealed by in situ differential electrochemical mass spectrometry,offering in-depth insights for comprehending the function of cathode additives.In addition,this breakthrough has been successfully utilized in high performance lithium/potassium ion capacitors with Li_(2)C_(2)O_(4)/K_(2)C_(2)O_(4) as pre-metallation reagent,which will convincingly promote the commercialization of MICs.

[Co(NH_3)_6]_2[Cd_8(C_2O_4)_(11)(H_2O)_4]·8H_2O: A 5-connected sqp topological metal-organic framework co-templated by Co(NH_3)_6^(3+) cation and (H_2O)_4 cluster

In our efforts to construct new metal-organic frameworks （MOFs） by template-directing method, a new cadmium oxalate, [Co（NH3）612[Cds（C204）ll（H20）4].8H20 （denoted HNU-1 ）, has been synthesized under hydrothermal condition in the presence of C0（NH3）6C13, The crystal structure of HNU-1 was determined by single-crystal X-ray diffraction （monoclinic, C2/c）, a = 11.126（2）A, b = 17.361 （4）,A, c = 16.119（3）A, fi = 102.40（3）, V = 3040.8（10） A and Z = 8. The open framework of HNU-1 contains 12-ring channels and exhibits a 5-connected sqp topological network with dinuclear Cd（ll） clusters acting as nodes. The Co（NH3）63＋ cations and unusual hydrogen-bonded （H20）4 clusters are found in the 12-ring channels with an alternative arrangement. It is believed that the （H20）4 clusters play a co-templating role in the crystallization of HNU-1.