*3.3. Techniques*

Transmission electron microscopy (TEM) observations were carried out using JEM 1400 JEOL Co. microscope, at 120 kV acceleration voltage. The samples were obtained by casting aqueous (or ethanol) solution of palladium nanoparticles onto a carbon coated nickel microgrid (200 mesh) and air-dried overnight. The thermogravimetric (TG) measurements of PdNPs/4-MePy were performed

with thermogravimeter Q50-1261 TA Instruments (USA) under nitrogen flow (6 dm<sup>3</sup>/h), heating rate = 10 K/min. Weight loss during thermal decomposition of PdNPs/4-MePy was determined in the temperature range 40–600 ◦C. TG measurements were performed in platinum pan, and the weight of the sample was around 1–2 mg. Results presented in this paper are the arithmetic mean of three repetitions, and the difference of results in a series of determinations of the sample was up to 2%.

### *3.4. Carbonylation of Aniline by CO*/*CO2*/*O2 to N,N'-Diphenylurea*

The procedure described elsewhere [15] was applied with some modifications. Briefly, the reaction was carried out in a 200 mL stainless-steel autoclave equipped with magnetic stirrer. Before the experiment, the autoclave was heated at 120 ◦C for 3 h (evaporation of water in order to avoid shifting the balance to the left, which may occur in the presence of an excess of water at high temperature) and cooled down to room temperature. Subsequently, one of the following catalysts: PdCl2(XnPy)2, PdCl2, Pdblack, or PdNPs (0.056 mmoL), and Fe powder (0–2.7 mmoL) were placed in the autoclave, the air was evacuated, and the system was filled with purified argon. Then, under a gentle stream of argon, other reagents and solvents were added: I2 (0–0.39 mmoL), aniline (54 mmoL), ethanol (20 mL), and optionally Py or XnPy (6.2 mmoL). After getting its cover closed, the autoclave was directly filled with molecular oxygen (0.6 MPa), a mixture of carbon dioxide and carbon monoxide (pressure of CO2/CO = 3.4 MPa), then placed in a hot oil bath, and kept at 80–140 ◦C for 15 or 60 min, depending on the reaction. After 15 or 60 min (depending on the reaction), the autoclave was cooled in a water bath, and then vented. The solid phase obtained after centrifugation (15,000 rpm for 15 min) in the form of white needles (with traces of precipitated palladium black) was re-crystallized from methanol and analyzed by elemental analysis, IR and 1H NMR. N,N-diphenylurea was identified on the basis of elemental analysis % (exp./calc.): C(73.60/73.57), H (5.75/5.70), N (13,22/13.20); FT-IR (KBr): 3326, 3283(s) νNH; 3000–3100 (s) νC-H aromat; 1648 (s) νC = O; 1595, 1555 (m) νC = Caromat; 1496, 1444 (m) νN-H; 1313, 1233 (m) νC-N; 755, 697 (s) νC-Haromat cm<sup>−</sup>1. M.P. = 235–237 ◦C; 1H NMR (300 MHz, DMSO): δ (ppm): 8.65 (s, 2 H), 7.46 (d, 4 H), 7.28 (t, 4 H), 6.97 (t, 2 H), and obtained values are in agreemen<sup>t</sup> with literature data [67]. Analysis of the liquid phase was performed using gas chromatography (GC-FID, GC-MS). Calculation of conversion of aniline was based on GC-FID analysis with n-decyl alcohol as standard.
