Pyridinium-Functionalized Ionic Metal–Organic Frameworks Designed as Bifunctional Catalysts for CO₂ Fixation into Cyclic Carbonates

Abstract

Ionic metal−organic frameworks (MOFs) offer a new platform to design and construct complete heterogeneous bifunctional catalytic systems for the chemical fixation of CO 2 with epoxides. Herein, we developed a series of bifunctional pyridinium ionic MOF heterogeneous catalysts (66Pym-RXs and 67BPym-MeI) by the postsynthetic N-alkylation of noncoordinated pyridine sites in porous MOFs. The synergetic catalytic effect of acidic sites with nucleophilic anions in the ionic MOF significantly enhanced the catalytic activity toward the cycloaddition of CO 2 with epoxides to produce cyclic carbonates under cocatalyst-free and solvent-free mild conditions. The catalytic activity of ionic MOFs is easily tuned by the introduction of different alkyl groups into pyridinium cations and halide ions. The 66Pym-iPrI catalyst displayed the highest catalytic performance in terms of the turnover number value for the synthesis of cyclic carbonates. The proposed alternative method provides the means of developing functional N-heterocyclic groups for the new design of bifunctional ionic MOFs as potential heterogeneous catalysts for CO 2 fixation applications.

Rational Design of a ZnII MOF with Multiple Functional Sites for Highly Efficient Fixation of CO2 under Mild Conditions: Combined Experimental and Theoretical Investigation

“…[13] However, most of the MOF-based catalysts reported so far require harsh reactionc onditions, for example, high pressure of CO 2 and/or high temperature. [14,15] An ideal catalyst for CO 2 fixation at milder conditions should have a high density of CO 2 -philic sites such as ÀNH 2 , ÀNH, ÀF, ÀN= N [16,17] along with Lewis-/Brønsted-acidic catalytic sites for combined selective capture and conversion. Herein, we report the synthesis of an ovel hydrogen-bonded3 Df ramework by incorporatingm ultiple functional sites, that is, aZ n II center,p olar (À CF 3 )g roups from ad icarboxylate ligand (hfipbba = 4,4'-(hexaflouroisopropylene)bis(benzoica cid)), and basic amine (ÀNH 2 ) groups from the melamine (MA) co-ligand (Scheme 1).…”

Building N‐Heterocyclic Carbene into Triazine‐Linked Polymer for Multiple CO2 Utilization

“…As shown in Table 2, NHC−CO 2 ‐Triazine@polymer1 displayed a good swelling property in these epoxides, and all epoxides were effectively converted into the corresponding cyclic carbonates in high yields (89–98 %). Notably, even for the large‐sized phenyl glycidyl ether and styrene oxide, which have been found to be inactive in many heterogeneous catalytic systems, [34,68] NHC−CO 2 ‐Triazine@polymer1 could also effectively catalyze their cycloadditions with CO 2 . These results demonstrate that the swelling property of NHC−CO 2 ‐Triazine@polymer1 enables this polymeric catalyst work like a quasi‐homogeneous catalyst and benefits the access of large‐sized reactants to the catalytic sites within the polymer, promoting its catalytic activity in the cycloaddition reaction of CO 2 with various epoxides.…”

Metal–Organic Frameworks Based on Group 3 and 4 Metals

“…[165] Moreover, a lot of similar Zr-MOFs with fcu topology have been documented in past two years. [166][167][168][169][170][171][172][173][174][175][176] Linker elongation is one of the most important strategies to obtain MOFs with large pore sizes. However, fcu Zr-MOFs tend to interpenetrate with increase of linker sizes.…”

“…For example, VPI-100, NU-903, NU-904, NU-1008, MOF-892, MOF-893, PCN-224(Co)-BPDC-R 7 , 66Pym-iPrI, ZSF-1, ZSF-2, and Zr-TzTz have been used as catalysts for the chemical fixation of CO 2 with the maximum conversion up to almost 100%. [165,171,176,180,215,238,248] In addition, ethylene dimerization or oligomerization were also catalyzed by nickel containing Zr-MOFs, PCN-160-47%Ni, HUST-2, HUST-3, HUST-4, and NiCl@DUT-133, with high conversion yields and selectivity. [168,187,255] Farha and co-workers also [241] Copyright 2019, American Chemical Society.…”