Metal–Organic Frameworks Significantly Enhance Photocatalytic Hydrogen Evolution and CO₂ Reduction with Earth-Abundant Copper Photosensitizers

Abstract

We report here the design of two multifunctional metal−organic frameworks (MOFs), mPT-Cu/Co and mPT-Cu/Re , comprising cuprous photosensitizers (Cu-PSs) and molecular Co or Re catalysts for photocatalytic hydrogen evolution (HER) and CO2 reduction (CO2RR), respectively. Hierarchical organization of Cu-PSs and Co/Re catalysts in these MOFs facilitates multielectron transfer to drive HER and CO2RR under visible light with an HER turnover number (TON) of 18 700 for mPT-Cu/Co and a CO2RR TON of 1328 for mPT-Cu/Re, which represent a 95-fold enhancement over their homogeneous controls. Photophysical and electrochemical investigations revealed the reductive quenching pathway in HER and CO2RR catalytic cycles and attributed the significantly improved performances of MOFs over their homogeneous counterparts to enhanced electron transfer due to close proximity between Cu-PSs and active catalysts and stabilization of Cu-PSs and molecular catalysts by the MOF framework.

Synergistic photoredox and copper catalysis by diode-like coordination polymer with twisted and polar copper–dye conjugation

“…In practice, photoredox and copper catalysis are usually compromised by adopting the high loadings of Cu(I) precursors to kinetically balanced off the excited-state quenching effect of in situ generated Cu(II) ions 6 – 8 . Thinking outside the box by a manner of aggregation state, the crystalline porous coordination polymers 9 , 10 fix photosensitizers and copper(II) ions in high local concentrations and spatially isolate them to block the futile intermolecular fluorescence quenching (Fig. 1b ).…”

A Simple Ni‐based Metal–organic Framework as Catalyst for Dye‐sensitized Photocatalytic H2 Evolution from Water Reduction

“…They have already been widely applied in gas separation/adsorption (15,16), capacitors (17–19), catalysis (20,21), and so on. In photocatalysis fields, there have been some studies on application of MOF in photo‐decomposition of organic dyes pollutants (22–24) and photocatalytic organic reactions (25–27) and water splitting (28–30). For example, regarding water splitting into H 2 gas by using MOF‐related photocatalysts, Rosseinsky et al (31) synthesized a water‐stable porous aluminoporphyrin‐based MOF (Al‐PMOF) with a large BET surface area of 1200 m 2 g −1 ; the material achieved a highly efficient hydrogen production of 200 µmol h −1 with Pt as a co‐catalyst via a LMCT (ligand‐to‐metal charge transfer) mechanism.…”

Charge-Transfer Regulated Visible Light Driven Photocatalytic H2 Production and CO2 Reduction in Tetrathiafulvalene Based Coordination Polymer Gel

“…29 CH 4 formation is thermodynamically favourable (E 0 = -0.24 V versus RHE at pH=7) than CO formation (E 0 = -0.53 V versus RHE at pH=7) 30,31 as the former reaction takes place at a lower potential. Nevertheless, from a kinetic point of view, the eight-electron reduction of CO 2 to CH 4 is more di cult especially under photochemical condition than the two-electron reduction of CO 2 to CO. 32 To address challenges associated with photochemical H 2 production and CO 2 reduction, a novel photocatalytic system needs to be developed by the innovative design of photosensitizer and catalytic moiety. 33,34 Recently, carbon-nitride based photocatalyst for H 2 evolution and CO 2 reduction to CO has been reported.…”