Piezoelectrically enhanced charge carriers transfer in a highly conjugated nickel(II)-acetylide framework for photocatalytic CO₂ reduction

Abstract

The piezoelectric field within two-dimensional (2D) piezo-photocatalysts offers a promising strategy for enhancing charge carrier kinetics to convert CO2 into valuable chemicals. However, the diversity of available 2D piezo-photocatalysts remains limited. Here, we present a highly conjugated NiII-acetylide framework (HETP-Ni-GY) featuring triangular atomic pores arranged in a hexagonal symmetry, constructed by incorporating NiII-complex into the graphdiyne (GDY) framework via NiII-bis(acetylide) linkages (–C≡C–Ni(PEt3)2–C≡C–). The triangular topology induces a densely packed yet ordered π-structure that facilitates efficient electron transfer. The synergistic interplay of light and piezoelectric field in the HETP-Ni-GY/triethanolamine (TEOA) catalytic system enables the efficient production of CO (129.80 μmol g–1 h–1) and CH4 (10.08 μmol g–1 h–1), with a total selectivity of 78.44%. Experimental and theoretical studies reveal that the NiII-(PEt3)2 units within the framework significantly enhance piezoelectric polarization (e11 = 2.46 × 10–10 C m–2, d33 = 4.91 pm V–1) due to increased structural distortion and noncentrosymmetry, facilitating the conversion of CO2. The triphenylene π-columns function as electron reservoirs, while NiII-bis(acetylide) blocks serve as CO2 capture and activation centers through π-d-π interactions. This study provides fundamental insights into the functionality of low-cost metal-acetylide frameworks and offers guidance for the rational design of efficient 2D piezocatalysts.