Solid-state phase transformations toward a metal-organic framework of 7-connected Zn_(4)0 secondary building units

In the development of metal-organic frameworks(MOFs),secondary building units(SBUs)have been utilized as molecular modules for the construction of nanoporous materials with robust structures.Under solvothermal synthetic conditions,dynamic changes in the metal coordination environments and ligand coordination modes of SBUs determine the resultant product structures.Alternatively,MOF phases with new topologies can also be achieved by post-synthetic treatment of as-synthesized MOFs via the introduction of acidic or basic moieties that cause the simultaneous cleavage/reformation of coordination bonds in the solid state.In this sense,we studied the solid-state transformation of two ndc-based Zn-MOFs(ndc=1,4-naphthalene dicarboxylate)with different SBUs but the same pcu topology to another MOF with sev topology.One of the chosen MOFs with pcu nets is[Zn_(2)(ndc)_(2)(bpy)]_(n)(bpy=4,4,-bipyridine),(6C_(bpy)-MOF)consisting of a 6-connected pillared-paddlewheel SBU,and the other is IRMOF-7 composed of 6-connected Zn40(C 00)6 SBUs and ndc.Upon post-structural modification,these pcu MOFs were converted into the same MOF with sev topology constructed from the uncommon 7-connected Zri_(4)O(COO)_(7)SBU(7C-MOF).The appropriate post-synthetic conditions for the transformation of each SBUs were systematically examined.In addition,the effect of the pillar molecules in the pillared-paddlewheel MOFs on the topology conversion was studied in terms of the linker basicity,which determines the inertness during the solid-state phase transformation.This post-synthetic modification approach is expected to expand the available methods for designing and synthesizing MOFs with controlled topologies.

A novel benzo[4,5]furo[3,2-d]pyrimidine-based host as a n-type host for blue phosphorescent organic light-emitting diodes

An electron-transport-type host was synthesized using a benzo[4,5]furo[3,2-d]pyrimidine(BFP)core to develop a high triplet energy host.The host was designed to have both the tetraphenylsilyl blocking group and the hole-transport-type carbazole group.In the device application,the host was used as an electron-transport-type host mixed with a hole-transport-type 3,3'-di(9H-carbazol-9-yl)-1,1†-biphenyl(mCBP)host in the blue phosphorescent organic light-emitting diodes(PhO-LEDs)doped with a[[5-(1,1-dimethylethyl)-3-phenyl-1H-imidazo[4,5-b]pyrazin-1-yl-2(3H)-ylidene]-1,2-phenylene]bis-[[6-(1,1-dimethylethyl)-3-phenyl-1H-imidazo[4,5-b]pyrazin-1-yl-2(3H)-ylidene]-1,2-phenylene]iridium(Ir(cb)3)blue phosphor.As a result,the mCBP:CzBFPmSi mixed host showed high external quantum efficiency over 20%at 1000 cd m^(−2) and low efficiency roll-off in the blue PhOLEDs.