Piperazine-Linked Metalphthalocyanine Frameworks for Highly Efficient Visible-Light-Driven H₂O₂ Photosynthesis

Abstract

Artificial photosynthesis of H2O2 from O2 reduction provides an energy-saving, safe, and green approach. However, it is still critical to develop highly active and selective 2e– oxygen reduction reaction photocatalysts for efficient H2O2 production owing to the unsatisfactory photosynthesis productivity. Herein, two new two-dimensional piperazine-linked CoPc-based covalent organic frameworks (COFs), namely, CoPc-BTM-COF and CoPc-DAB-COF, were afforded from the nucleophilic substitution reaction of hexadecafluorophthalocyaninato cobalt(II) (CoPcF16) with 1,2,4,5-benzenetetramine (BTM) or 3,3′-diaminobenzidine (DAB). Powder X-ray diffraction analysis in combination with electron microscopy and a series of spectroscopic technologies reveals their crystalline porous framework with a fully conjugated structure and eclipsed π-stacking model. Ultraviolet–visible diffuse reflectance absorption spectra unveil their excellent light absorption capacity in a wide range of 400–1000 nm. This, together with their enhanced photo-induced charge separation and transport efficiency as disclosed by photocurrent response and photoluminescence measurements, endows the as-prepared piperazine-linked CoPc-based COFs with superior photocatalytic activity toward O2-to-H2O2 conversion under visible-light irradiation (λ > 400 nm). In particular, CoPc-BTM-COF exhibits a record-high H2O2 yield of 2096 μmol h–1 g–1 among the COF-based photocatalysts and an impressive apparent quantum yield of 7.2% at 630 nm. The present result should be helpful for fabricating high-performance and low-cost photocatalysts for visible-light-driven H2O2 photosynthesis.

Integrating Bifunctionality and Chemical Stability in Covalent Organic Frameworks via One-Pot Multicomponent Reactions for Solar-Driven H2O2 Production

“…All COFs exhibit an O 2 sorption interaction near the triazine core [(CH···O: 2.72 Å; DMCR-1 ), (CH···O: 2.54 Å; DMCR-1NH ), and (CH···O: 2.88 Å; Imine-1 )]. A similar intermolecular distance was reported between O 2 and CoPc-BTM-COF (N···O: 2.66 Å) and O 2 and EBA-COF (CH···O: 2.73 Å) using DFT calculations. Both DMCR COFs have additional adsorption sites for oxygen via their −COOH groups [(OH···O: 2.61 Å; DMCR-1 ) and (OH···O: 3.06 Å; DMCR-1NH )].…”

Deciphering the Roles of Diketone-Derived Defects on Graphite Carbon Nitride in Boosted Photocatalytic Production of H2O2

“…53 It is noteworthy that the peak area ratio between N 2C and N 3C was significantly decreased from 1.93 of the pristine CN to 1.61 of A 0.05 CN (Figure 3d), suggesting that the C replacement occurred majorly at the N 2C site. 34,36 The loss of N 2C and the introduction of C−OH led to the formation of the dual defects (C doping and surface −OH modification). 54 The presence of the heptazine structure and the nature of the defects were further investigated with 13 C NMR.…”

“…The light intensity at 420 nm was 100 mW·cm –2 . The AQY was calculated by dividing the number of produced H 2 O 2 molecules with the number of incident photons . A factor 2 was used to justify the stoichiometric ratio of H 2 O 2 production to photon absorption.…”

Covalent Organic Framework/g-C3N4 van der Waals Heterojunction toward H2 Production

“…Recently, covalent organic framework (COF) is an emerging type of platform material capable of solar–chemical energy conversion. It features ordered pore structure, significant specific surface area, controllable skeleton structure, and small band gap. , Moreover, the extended π-conjugated structure in COF is beneficial to accelerating the charge carrier transfer along the in-plane and out-of-plane stacking directions, which enables the fast transfer of photogenerated carriers . However, until now, the photocatalytic activity is still far from the expectation in the reported literature studies because of its structural periodicity, and it is certainly not easy for a single COF to possess all necessary conditions for an efficient photocatalytic reaction.…”