Rapid and highly selective conversion of CO2 to methanol by heterometallic porous ZIF-8

Abstract

Commercial application of CO2-to-fuel technology has been mainly restricted due to low-cut CO2 adsorption and activation by photocatalyst, thus contributing to low/impure fuel yield. Defect engineering of key CO2 activators onto excellent CO2 adsorbent along with in-situ & co-production of Hadatoms could address these issues. Herein, we report rapid conversion of CO2 to CH3OH in a photocatalytic system composed of CoxMoyZn1−x−yZIF-8 photocatalyst and NaBH4-assisted Hadatoms production. Doping of Co & Mo into ZIF-8 provided active centers for CO2 activation and structured highly efficient electron transport chains (ETCs) for selective conversion of continuous supply of CO2 into CH3OH (99%). Conversion of CO2 by CoxMoyZn1−x−yZIF-8 yields 9.96 mmole gcat-1 h-1 of CH3OH higher than reported ZIF-8 based photocatalyst in literature, and pristine ZIF-8, which only produced 94.2 µmole g-1 of carbon monoxide. Mechanistically, engineered doping of Co0.25/Mo0.25 in Zn-ZIF-8 enhanced visible light absorption and mechanized ETCs due to d-orbitals and multiple redox states, which largely expediated CO2 adsorption-activation. While in-situ & co-production of Hadatoms from NaBH4 and water spitting boost conversion of activated CO2 to CH3OH. Interestingly, the controlled release of Hadatoms from NaBH4 maintained a requisite charge gradient across ETCs, which was proven to be another reason for the high yield and selectivity of CH3OH.13CO2 analysis confirmed the source of C in CH3OH was supplied CO2, not by photocatalyst carbon that proved the stability of CoxMoyZn1−x−yZIF-8. We believe this work will be a step forward for commercializing revolutionary CO2-to-fuel technology, while results and novel interpretation will be key for multidisciplinary research.