Efficient and Selective Methane Borylation Through Pore Size Tuning of Hybrid Porous Organic‐Polymer‐Based Iridium Catalysts

Abstract

As an ew energy source that could replace petroleum, the global reserves of methane hydrate (combustible ice) are estimated to be approximately 20 000 trillion cubic meters. Alarge amount of methane hydrate has been found under the seabed, but the transportation and storage of methane gas far from coastlines are technically unfeasible and expensive.T he direct conversion of methane into value-added chemicals and liquid fuels is highly desirable but remains challenging.Herein, we prepare as eries of iridium complexes based on porous polycarbazoles with high specific areas and good thermochemical stabilities.T hrough structure tuning we optimized their catalytic activities for the selective monoborylation of methane.O ne of these catalysts (CAL-3-Ir) can produce methyl boronic acid pinacol ester (CH 3 Bpin) in 29 %y ield in 9hwith aturnover frequency (TOF) of approximately 14 h À1 . Because its pore sizes favor monoborylated products,i th as ah igh chemoselectivity for monoborylation (CH 3 Bpin:CH 2 -(Bpin) 2 = 16:1).

Downsizing of Block Polymer-Templated Nanopores to One Nanometer via Hyper-Cross-Linking of High χ–Low N Precursors

“…Since control of micropore size is not trivial for microporous polymers, particularly those with amorphous frameworks, this straightforward control of pore size provided by the block polymer-based approach will be highly beneficial to achieve size selectivity for small molecules . Such size discrimination ability of microporous polymers has only been demonstrated by the well-defined porous polymer fabricated via lyotropic liquid crystal or peptide self-assembly. − A few examples have also highlighted the improved selectivity factor for gas separation and size-dependent chemoselectivity for heterogeneous catalysis …”

“…14−16 A few examples have also highlighted the improved selectivity factor for gas separation 17 and size-dependent chemoselectivity for heterogeneous catalysis. 18 There are two fundamental thermodynamic issues against pushing the block polymer strategy to the synthesis of microporous polymers. In order to induce microphase separation, the constituting blocks should be sufficiently incompatible.…”

Selective monoborylation of methane by metal–organic framework confined mononuclear pyridylimine-iridium(i) hydride

“…21 Despite significant progress in developing catalysts for selective monoborylation of methane, these catalytic systems also generate a considerable amount of boron-byproducts such as HOBpin, pinBOBpin and Sol-Bpin during the borylation reactions. [22][23][24] Herein, we report a MOF-confined mononuclear pyridylimine-ligated iridium(I)hydride, which is a highly robust and active heterogeneous catalyst for chemoselective monoborylation of methane to afford CH 3 Bpin in a near-quantitative yield (Fig. 1).…”