Constructing chemical stable 4-carboxyl-quinoline linked covalent organic frameworks via Doebner reaction for nanofiltration.

Covalent linkages are the key component of covalent organic frameworks (COFs). The development of stable and functional linkages is essential to expand the COFs family and broaden their application prospects. In this work, we report the synthesis of crystalline and chemical stable 4-carboxyl-quinoline linked COFs (QL-COFs) via Doebner reactions in both one-pot (OP) and post-synthetic modification (PSM) methods. Both methods can be universally applied to most of the reported imine COFs family via bottom-up construction or linkage conversion. Owing to the contractive pore size, more hydrophilic structure and better chemical stability than the conventional imine COFs endowed by 4-carboxyl-quinoline linkage, QL-COFs are supposed to possess a wider application range. We further demonstrate the nanofiltration membrane (NFM) based on QL-COF exhibited a desirable separation capacity with high rejection for small dye molecules (> 90%), high water permeance (850 L m-2 h-1 MPa-1) and tolerance of extreme conditions (1 M HCl/NaOH), which were benefitted from the enhanced properties of QL-COFs. Additionally, efficient ion sieving properties were also achieved by QL-COF membrane. We anticipate that this work opens up a way for the construction of robust and functional COFs materials for practical applications.

Coordination Polymer Derived Porous Carbon Activated in Situ by the ZnCl2 Dot: Capacitances Greatly Enhanced by Redox-Activity Additives in Electrolytes.

Herein, a 1D zinc coordination polymer [Zn(bibp)Cl2]∞ (CP-2-ZX) was assembled from the reaction of 4,4'-bis(imidazol-1-yl)-biphenyl (bibp) with ZnCl2. Through a calcination-thermolysis strategy, sponge-like highly porous carbon AC-Zn-CP was prepared by employing the coralloid sample of CP-2-ZX as the precursor. For comparisons, a series of activated carbon (AC-n) was obtained by the similar heating process on the mixture of bibp with ZnCl2 at different mass ratios. The results illustrate that the atomically dispersed ZnCl2 dot in the 1D chain of CP-2-ZX has an in situ activation effect on the generation of AC-Zn-CP, which can greatly promote the porosity and achieve high-efficiency utilization of ZnCl2. Therefore, the atomically dispersed activating agent provides a new method for environmentally friendly production of porous carbon materials. Significantly, the AC-Zn-CP electrode displays specific capacitance of 215 F g-1 in 3 M KOH solution, which will be largely promoted to 1419 F g-1 in the redox active electrolyte of K3[Fe(CN)6]/KOH. AC-Zn-CP also shows remarkable cycling stability (the capacity retention is 89.0% after 5000 cycles). Moreover, the fabricated symmetric supercapacitor owns a high energy density of 34.8 Wh kg-1 at 785.5 W kg-1. So, the AC-Zn-CP∩K3[Fe(CN)6] system has wide application prospects in supercapacitors.