Electron deficient boron-doped amorphous carbon nitride to uphill N2 photo-fixation through π back donation

The photocatalytic Nitrogen fixation to NH 3 by using water as a protonation source is a requisite renovation for life. Albeit, the activation and adsorption of robust N N is the bottleneck in NH 3 synthesis. Here, we report an amorphous-wrinkled hollow-tubular electron-deficient boron-doped carbon nitride (BCN) for improved photocatalytic N 2 fixation via “σ donation and π back donation”. The electron-deficient B played synergetic roles to activate and stabilize the adsorbed N 2 i.e. (i) It tunes the bandgap of CN for effective light absorption and charge transfer; (ii) The B-N coordination site polarizes chemisorbed N 2 via electron pair acceptance; (iii) The filled sp 2 orbital of B activates the N 2 by π-back donation. Consequently, the photocatalytic performance of BCN-4 reaches 0.93mmolh -1 g -1 with AQY of ~13% (350 nm) and solar to NH 3 conversion efficiency (SSC NH3 ) of 0.017%. The in situ DRIFT and DFT studies revealed that BCN exhibited spontaneous N 2 adsorption and activation, followed by protonation of the adsorbed N 2 , with a negligible energy barrier. The data that support the findings of this study are available in the supplementary material of this article. • Salt template approach has been applied to synthesize a porous hollow tubular BCN. • Metallomimetic B chemisorbs and activates N 2 in light along with bandgap adjustment. • The macro and mesopores in CN facilitate light absorption and charge transfer. • Excellent photocatalytic NRR rate (0.92 mmol) and AQY (13%) is achieved by B doping. • Electron deficient B selectively promotes N 2 reduction by suppressing proton adsorption.