Incorporating Catalytic Units into Nanomaterials: Rational Design of Multipurpose Catalysts for CO₂ Valorization

Conspectus CO2 conversion tovaluable chemicalsis effective atreducing CO2 emissions. We previously proposed valorization strategies and developed efficientcatalysts to address thermodynamic stability and kinetic inertnessissues related to CO2 conversion. Earlier, we developedmolecular capture reagents and catalysts to integrate CO2 capture and conversion, i.e., in situ transformation. Based on themechanistic understanding of CO2 capture, activation, andtransformation at a molecular level, we set out to develop heterogeneouscatalysts by incorporating catalytic units into nanomaterials viathe immobilization of active molecular catalysts onto nanomaterialsand designing nanomaterials with intrinsic catalytic sites. In thermocatalytic CO2 conversion, carbonaceous andmetal-organic framework (MOF)-based catalysts were developedfor nonreductive and reductive CO2 conversion. Novel Cu-and Zn-based MOFs and carbon-supported Cu catalysts were preparedand successfully applied to the cycloaddition, carboxylation, andcarboxylative cyclization reactions with CO2, generatingcyclic carbonates, carboxyl acids, and oxazolidinones as respectivetarget products. Reductive conversion of CO2, especiallyreductive functionalization with CO2, is a promising transformationstrategy to produce valuable chemicals, alleviating chemical productionthat relies on petrochemistry. We explored the hierarchical reductivefunctionalization of CO2 using organocatalysts and proposedstrategies to regulate the CO2 reduction level, triggeringheterogeneous catalyst investigation. Introducing multiple activesites into nanomaterials opens possibilities to develop novel CO2 transformation strategies. CO2 capture and insitu conversion were realized with an N-doped carbon-supported Zncomplex and MOF materials as CO2 adsorbents and catalysts.These nanomaterial-based catalysts feature high stability and excellentefficiency and act as shape-selective catalysts in some cases dueto their unique pore structure. Nanomaterial-based catalystsare also appealing candidates forphotocatalytic CO2 reduction (PCO2RR) and electrocatalyticCO(2) reduction (ECO2RR), so we developed a seriesof hybrid photo-/electrocatalysts by incorporating active metal complexesinto different matrixes such as porous organic polymers (POPs), metal-organiclayers (MOLs), micelles, and conducting polymers. By introducing Re-bipyridineand Fe-porphyrin complexes into POPs and regulating the structureof the polymer chain, catalyst stability and efficiency increasedin PCO2RR. PCO2RR in aqueous solution was realizedby designing the Re-bipyridine-containing amphiphilic polymer to formmicelles in aqueous solution and act as nanoreactors. We preparedMOLs with two different metallic centers, i.e., the Ni-bipyridinesite and Ni-O node, to improve the efficiency for PCO(2)RRdue to the synergistic effect of these metal centers. Sulfylphenoxy-decoratedcobalt phthalocyanine (CoPc) cross-linked polypyrrole was preparedand used as a cathode, achieving the electrocatalytic transformationof diluted CO2 benefiting from the CO2 adsorptioncapability of polypyrrole. We fabricated immobilized 4-(t-butyl)-phenoxy cobalt phthalocyanine and Bi-MOF as cathodes to promotethe paired electrolysis of CO2 and 5-hydroxymethylfurfural(HMF) and obtained CO2 reductive products and 2,5-furandicarboxylicacid (FDCA) efficiently.