Heterointerface regulation of covalent organic framework-anchored graphene via a solvent-free strategy for high-performance supercapacitor and hybrid capacitive deionization electrodes.

Covalent organic frameworks (COFs) with customizable geometry and redox centers are an ideal candidate for supercapacitors and hybrid capacitive deionization (HCDI). However, their poor intrinsic conductivity and micropore-dominated pore structures severely impair their electrochemical performance, and the synthesis process using organic solvents brings serious environmental and cost issues. Herein, a 2D redox-active pyrazine-based COF (BAHC-COF) was anchored on the surface of graphene in a solvent-free strategy for heterointerface regulation. The as-prepared BAHC-COF/graphene (BAHCGO) nanohybrid materials possess high-speed charge transport offered by the graphene carrier and accelerated electrolyte ion migration within the BAHC-COF, allowing ions to effectively occupy ion storage sites inside BAHC. As a result, the BAHCGO//activated carbon asymmetric supercapacitor achieves a high energy output of 61.2 W h kg-1 and a satisfactory long-term cycling life. More importantly, BAHCGO-based HCDI possesses a high salt adsorption capacity (SAC) of 67.5 mg g-1 and excellent long-term desalination/regeneration stability. This work accelerates the application of COF-based materials in the fields of energy storage and water treatment.

A longitudinally expanded Ni-based metal-organic framework with enhanced double nickel cation catalysis reaction channels for a non-enzymatic sweat glucose biosensor.

Nickel-based metal-organic frameworks (Ni-MOFs) have attracted increasing attention in non-enzymatic glucose sensing. However, the insufficient active Ni cation sites from a stacked MOF layer, the unclear Ni catalysis mechanism, and the severe liquid alkaline electrolyte remain challenging for practical applications. In this work, the sonication-induced longitudinal-expansion of Ni-MOFs increases the active nickel ion sites, which not only enhances the current response to glucose detection, but also shows the oxidation peak evolution of nickel ions with different sonication times, revealing the mechanism of different glucose detection channels. The Ni-MOF sonicated for 60 min (60 min Ni-MOF) displays enhanced Ni(iii)/Ni(ii) and more significant Ni(iv)/Ni(iii) double nickel cation channels for catalyzing glucose into glucolactone compared to the 0 min Ni-MOF (without sonication), showing optimized glucose detection ability with a high sensitivity of 3297.10 µA mM-1 cm-2, a low detection limit of ∼8.97 µM (signal-to-noise = 3) and a wide linear response range from 10 to 400 µM from the cyclic voltammetry test as well as a high sensitivity of 3.03 µA mM-1 cm-2, a low detection limit of ∼1.16 µM (signal-to-noise = 3) and a wide linear response range from 10 to 2000 µM from the chronoamperometry test. More importantly, an all-solid-state glucose biosensor using a PVA/NaOH solid-state electrolyte and a disposable 60 min Ni-MOF working electrode is assembled for non-enzymatic sweat glucose detection.