I apologize for the confusion caused by my previous response. Glucose formation is an exothermic process, not endothermic. The negative enthalpy of formation (ΔHof) value for glucose indicates that the formation of glucose from its constituent elements (carbon, hydrogen, and oxygen) releases energy.
The negative value of ΔHof (-1273.3 kJ/mol) means that 1 mole of glucose releases 1273.3 kJ of energy when it is formed under standard conditions (25 degrees Celsius and 1 atmosphere pressure) from its elements in their standard states. This energy release occurs due to the formation of chemical bonds in glucose, which are energetically favorable.
In general, negative enthalpy of formation values indicate exothermic processes, where energy is released, while positive values indicate endothermic processes, where energy is absorbed. Therefore, the formation of glucose is an exothermic process, and energy is released during its formation.