In the past years organic semiconductor photocatalysis has made the remarkable advances in developing efficient synthetic chemical routes to well refined structures. Until now, most efforts were focused on optimizing of the semiconductor photocatalyst, while solvents were largely ignored. Herein, we design a series of functional deep eutectic solvents (DES) with adjustable physicochemical properties - density, viscosity, glass transition temperature, and chemical activity towards reductive formylation of nitroarenes. The DES are prepared from abundant, sustainable resources, which makes them an affordable alternative to the ionic liquids, even on larger industrial scales. By combining the ammonium formate-based DES with carbon nitride photocatalyst, we enable the simultaneous six-electron reduction of nitrocompounds to the corresponding N-substituted formamides and benzimidazoles in one pot. (C) 2019 Elsevier Inc. All rights reserved.