Three-dimensional Co/Ni bimetallic organic frameworks for high-efficient catalytic ozonation of atrazine: Mechanism, effect parameters, and degradation pathways analysis

Scanning electron microscopy, linear sweep voltammetry, chronoamperometry, and in situ surface-enhanced Raman spectroscopy were used to investigate the electrochemical oxygen evolution reaction (OER) occurring on cobalt oxide films deposited on Au and other metal substrates. All experiments were carried out in 0.1 M KOH. A remarkable finding is that the turnover frequency for the OER exhibited by ∼0.4 ML of cobalt oxide deposited on Au is 40 times higher than that of bulk cobalt oxide. The activity of small amounts of cobalt oxide deposited on Pt, Pd, Cu, and Co decreased monotonically in the order Au > Pt > Pd > Cu > Co, paralleling the decreasing electronegativity of the substrate metal. Another notable finding is that the OER turnover frequency for ∼0.4 ML of cobalt oxide deposited on Au is nearly three times higher than that for bulk Ir. Raman spectroscopy revealed that the as-deposited cobalt oxide is present as Co(3)O(4) but undergoes progressive oxidation to CoO(OH) with increasing anodic potential. The higher OER activity of cobalt oxide deposited on Au is attributed to an increase in fraction of the Co sites present as Co(IV) cations, a state of cobalt believed to be essential for OER to occur. A hypothesis for how Co(IV) cations contribute to OER is proposed and discussed.

One of the outstanding challenges in the field of porous materials is the design and synthesis of chemical structures with exceptionally high surface areas. Such materials are of critical importance to many applications involving catalysis, separation and gas storage. The claim for the highest surface area of a disordered structure is for carbon, at 2,030 m2 g(-1) (ref. 2). Until recently, the largest surface area of an ordered structure was that of zeolite Y, recorded at 904 m2 g(-1) (ref. 3). But with the introduction of metal-organic framework materials, this has been exceeded, with values up to 3,000 m2 g(-1) (refs 4-7). Despite this, no method of determining the upper limit in surface area for a material has yet been found. Here we present a general strategy that has allowed us to realize a structure having by far the highest surface area reported to date. We report the design, synthesis and properties of crystalline Zn4O(1,3,5-benzenetribenzoate)2, a new metal-organic framework with a surface area estimated at 4,500 m2 g(-1). This framework, which we name MOF-177, combines this exceptional level of surface area with an ordered structure that has extra-large pores capable of binding polycyclic organic guest molecules--attributes not previously combined in one material.