Phenanthraquinone modified carbon quantum dots covalent-grafted onto Cu-MOF for photocatalytic CO2 reduction: Construction of dual-active sites and parallel charge channels based on the cooperation between photoexcitation and electron-entrap

How to coordinate the catalytic sites and the charge supply in CDs@MOFs hybrids to accelerate carriers transferring, suppress charge recombination and maximize charge transferring is a challenge. Here, the hybrid of PQ-CDs6.67@Cu-TCA fabricated by Cu-TCA (TCA = 4,4',4′'-nitrilotribenzoic acid) encapsulating 9,10-phenanthraquinone (9,10-PQ) modified carbon quantum dots (PQ-CDs), which was fully characterized and used for photocatalytic CO2 reduction. Covalent-bonding of CDs with the paddle-wheel Cu structure and 9,10-PQ provides parallel electron pathways for accelerating electron transferring and minimum carrier recombination. PQ-CDs6.67@Cu-TCA exhibited an excellent electron consumption rate (Rele) of 393.98 μmol·g−1·h−1 and a high CH4 yield of 44.43 μmol·g−1·h−1 with a selectivity of 90.22%, being far superior to most carbon materials/MOFs-based heterojunctions. Research evidences that through the parallel electron pathways, photon collection and transferring of PQ-CDs with optimal loading-amount meet chemical-producing Cu2+ and 9,10-PQ active centers, maximally improving electron utilization and suppressing the internal friction in PQ-CDs6.67@Cu-TCA.